You can sell it to other people and you can sell crypto market.
If you sell with other people not through the official market you should be careful, many people take advantage of panic from people who are in need of money.

Bitcoin and Altcoin are different types of coins but are interconnected with each other. If someone sells Altcoin is used to buy Bitcoin then Altcoin will experience a decline and Bitcoin will increase and vice versa.
that's what I have seen and observed so far.

it is possible, they want to manipulate the market to get a profit to fill their fat belly.

This is a big ordeal on Bitcoin, after we saw a few years ago.
Bitcoin always has a surprising increase and decrease, if by the end of 2018. Bitcoin can fly even higher after experiencing a decline. Maybe more and more investors will come and ask how to make a good investment in Bitcoin, next year.

Bitcoin is an independent Cryptocurrency that no other third party takes advantage of transactions from two sides. This is a peer to peer transaction conducted by sellers and buyers only. Cryptocurrency transactions do not need to be identified or verified by the recipient of the funds when the funds are sent, that is what makes many people choose to use bitcoin.

Does the government mix in managing transactions for each user?

If the government mixes in managing transactions, will they take advantage of every transaction

What is your opinion.?

If Cryptocurrency has been tracked, then the main Cryptocurrency destination will change.
The community creates Cryptocurrency, to make the currency easy to use by anyone and at any time without any intermediaries between one person and another.
If Cryptocurrency, has an institution that oversees every trade, who will pay them? and that will change the main purpose of the Community to make Cryptocurrency.

If you want to use Bitcoin for a trading business, I think it's a good idea.
Bitcoin has easy transactions, and an easy transaction will usually attract many customers to try doing it.
If you are sure of your knowledge of real market prices and cryptocurrency prices, why not try it.
Hope you are lucky and successful sir.

I just want bitcoin in the future to be a trading currency that can be used to buy all the necessities on the internet, only that is no more because if we buy goods with bitcoin everything becomes easier.

No matter how strong security is, there will always be hackers who can penetrate it, that is always in my mind.
For precautions :
01. Use your wallet according to what you need. If you trade you can make a special wallet to receive funds from the buyer and send money to trade.
02. Make a cold wallet in the sense that you make a wallet that only receives funds from your other account, and does not receive funds from other people so that it will minimize tracking your wallet from a thief.

When panic makes them start selling at low prices it is something that is valuable to us.
I prefer to take advantage of what they give and make the best use of it when prices start flying again. 

Predictions and speculations are needed, even experts continue to monitor and analyze markets to try to predict market prices.

The world is always ready to accept any challenge, It's just that support for Cryptocurrency still needs a lot of attention to embrace the whole world.

Yes, I agree about what you think, bitcoin is the largest virtual currency today and occupies the number one seat in every crypto market in the world.
If now Bitcoin has decreased, surely in a few months it will go to the top again.
So we don't need to panic when bitcoin has decreased.

The government does not dare to formalize bitcoin because the government does not have control over the activities carried out by bitcoin users.
I think that is what causes all governments not to dare to say that bitcoin is an official virtual currency