If you want to know more about this service, you just need to look, who is the registrant of this page.
https://www.whois.com/whois/crypto2018.club
Registrant is anonymous registered from Panama PO Box.
So, there is no trust on this site and the probability is high to get scammed.
There are so many exchangers around, where you can buy ETH and LTC with your Bitcoin like Cryptopia, Bittrex, Bitfinex and many more.

For beginners I would recommend cryptopia and Poloniex:
Cryptopia
Advantages
- Cryptopia has a lot of cryptocurrencies for trading
- Up to a withdraw limit of 5000 $ daily no ID verification is needed
- Cryptopia has many info sites about all listed cryptocurrencies
- Forum for info and chatbox for little coin presents and fun are implemented
- Arbitrage site is implemented
Disadvantages
- Many cryptocurrencies are "dead" coins in my opinion. Good research is needed for trading there.
- Interface especially for mobile devices is awful in my opinion.

Poloniex
Advantages
- Very handy interface on PC and all mobile devices.
- Mostly only established cryptocurrencies are listed.
- Useful charts in any cryptocurrency.
- Lending opportunity of several cryptocurrencies.
Disadvantages
- Awful slow support
- Now each user must go through ID verification.

Edit:. Registrants of the site with P.O. Box in Panama, fully anonymous and cheap script also able to damage devices with its "browser mining", if wanted or not.
Don't invest to this scheme. You will loose your money or wait years to get investment back.

Payment recieved for week one and two, many thanks.

We don't know, which cryptocurrency you tried to deposit. But mostly deposit issues on Cryptopia and other legit exchangers are caused by the network or wallets of deposited cryptocurrencies. It may be caused by overloaded network, wallets being under maintance or too low fees. If issues lay on network or upgrades, the coins will appear as soon the network  is working proper or the wallets are updated. There is no need to worry about. If you sent your funds with too low fees, it may be neccessary to accelerate your transfer.
Cryptopia itself usually credits every fund very fast.

Litecoin is called the Bitcoin Silver and has still much potential, but the future will be on cryptocurrencies with high privacy. Monero is one of them and eligible to keep savings safe in countries, where cryptocurrencies are banned. Monero can't be tracked and is based on a stable secure technology.  But in midterm it is no mistake to keep also Litecoin because of its awesome upgrade last year with cheap and fast transfers.

As preposters already stated, the trading volumen takes an important part on differences. But you must be careful. When prices are shown, that doesn't mean, that you can sell/buy cryptocurrencies for actual prices. You must study first bids and asks, they may differ significantly from each other, the lower the trading volumen is. Also manipulations by pumping groups may cause short price differences on exchangers, especially on exotic/new coins.
But to be honest, price differences of Bitcoin between 1000$ -2000$ are not usual.

Coinomi is a native multicoinwallet for Android. There also can be stored tokens, but I still didn't find out, how to automaticly get the tokens listed on Coinomi. I baught there also token as inApp feature, but forgot the name of the token. But there is an awesome feature, that lets export the ETH private key from Coinomi to myetherwallet. So I use both wallets in combination.

You will have several days to withdraw your coins, as preposter already stated. I think, also deposit should work, because you got several confirmations, before unobtanium will have been delisted.
You will have enough time to withdraw them and trade them on other exchangers.
https://coinmarketcap.com/currencies/unobtanium/#markets

What you mean, is called Trailing-Stop-Loss.. The only exchanger, I found, that is supporting trailing stop orders is Bitfinex
https://support.bitfinex.com/hc/en-us/articles/115003506545-Trailing-Stop-Order
Unfortunately this order is only possible at margin trading.
But there are trading bots, that support dynamic orders on exchangers, for example gunbot.

The cause of this crash was most probably bad press about upcoming "bans" in Korea and China and a correction, that happens at beginning of every year. But crashes may also be caused by single cryptocurrencies, by exchangers or by criminal acts. It is important to figure out the reason of any bigger movements, because consequences by traders may differ by reasons.
Day traders need to monitor movements multiple times a day. But for longterm trades it is important to research all cryptocurrencies before investment. In my opinion there is no need, if not destructive, to watch all news and movements daily. Well established cryptocurrencies don't follow the movements of traditional markets, because their potential is still at beginning.

Securecoin seems to have pumps every few months like you can see on its history on coinmarketcap.
https://coinmarketcap.com/currencies/securecoin/historical-data/?start=20170118&end=20180118
I don't know, how much you paid, so its hard to predict, whether it will recocer to that price, you baught. Generally the prognosis will not be positive, because you seem to have baught it on its highest point. Maybe you got the advice from members of pumping dumping group. That is illegal, but unfortunately there are many groups around, who arrange orchestred buys at a certain time and post in chats to engage victims to buy that coin and those cheaters suddenly sell and leave cheated buyers with big loss.
If it is so, it would be helpful, to know their usernames on trollbox and report them to cryptopia.

Better describe your issue, that we can give you helpful advices.
Else this guide of poloniex may help you to open support tickets in the right way and get help:
https://poloniex.freshdesk.com/support/solutions/articles/1000244852-my-withdrawal-status-is-complete-error-what-now-

Yes, as preposters already stated, there are multicoin wallets with integrated exchangers for example on jaxx and coinimi for android. They are safe in my experience, because you own your private keys, but there are aspects, you should be aware.
You must pay at each exchange transfer fees and mostly additional exchange fees.
The leading (only?) exchangers are shapeshift and changelly.
When I use shapeshift, I only exchange cryptocurrency pairs with low transactions fees like Dogecoin and Litecoin.
I used changelly, but wouldn't do that again within Coinomi, because the exchange rates are not shown before exchange button is clicked. There are shown rates, but they can change during transfer, that is proceeded quite long. So I never know, if I am making a good or bad deal. They should change that and take shapeshift's procedure as example.

There are several ways to protect portfolio from market crash:
1. Devide your portfolio in at least five cryptocurrencies.
2. Hold your funds and stop trading during crash or ....
3. ... don't hold and look for cryptocurrencies with little movements or ...
4. ... exchange your BTC/Altcoins into USDT during crash and buy them back later.
5. Don't watch your funds during crash. This may prevent panic sell.
6. Analyse cause of crash and search cryptocurrencies, that are not affected (I didn't find any. But maybe you have more luck )

There would only be a very little chance to get back stolen ETH. Maybe the ETH address can be tracked to an exchanger. If so, exchanger could freeze the account of the hacker.
Although its concerned to ETH, I would ask at the technical support here on Bitcointalkforum
https://bitcointalk.org/index.php?board=4.0
or supoort of myetherwallet, if there would be a chance to track the transaction to a deposit address of an exchanger or a service site.

Please remove.

For 20.000 $ I would defenetivly choose a token of a promising ICO project or Dogecoin, if I only would be allowed to take one cryptocurrency.
Why ICO project?
1. The crypto market gives an awesome opportunity to invest directly into a meaningful project.
2. Possible high longterm profits.
3. Be part of innovative developments connected with traditional services.
Why Dogecoin?
1.Transfers are fast, stable and cheap.
2. Dogecoin is not limited and has a reasonable inflation factor. So it also can stand high popularity and demands.
3. Dogecoin is still cheap and is still at beginning of its potential.
But nevertheless I would keep Dogecoin at midterm until regulations of governments are still moderate.
Later I would move to a decentralized cryptocurrency with high privacy like Monero.

I have a few suggestions:
Bitcoin: Bitcoin is unstoppable. The worldwide community is too strong against manipulations by traditional finance sector and governments.The innovation of blockchain can't be destroyed like internet. Third parties are not needed for payments.
Dogecoin: It recovered fast from the general crash of cryptocurrencies. It also gives a nice opportunity to lend on Poloniex. If you have the opportunity for an account on Polonoiex, lend them for 1% daily. The margin traders are speculating much on Doge so they pay the rates.
Monero: In my opinion Monero will one of the leading cryptocurrencies in near future. More and more governments will try to take influence to cryptocurrencies and track all citizens, who hold cryptocurrencies. Monero has proven high privacy and can be used in case of a ban of cryptocurrencies.
Ethereum: Ethereum has one of the most interesting platforms for innovative projects and crowd funding (ICO-projects)
ICO tokens:: There are many scam projects, but also promising ICOs coming with innovative  projects. These kind of investments need a good research to gain great profits.
I would generally recommend well established decentralized altcoins for long term portfolio.

I am just wondering, that altcoins fall with BTC in relation to altcoin/BTC. But as nearly all cryptocurrencies are affected, we just need to wait one or two days for recovering. If we would have expected the deep fall, we would have gained much profits in exchanging to USDT today and buy again on deepest point.