The current market corrections are making a better investor, well weeding out the panicky investors that do not do their research. The hype balloon has been pretty deflated lately, making it easier to find legitimate projects to come to the surface. To top it off i don't have to read "when moon! when lambo!" every time i open discord or telegram. I think those are huge benefits.

There are Bitcoin, and also there are Bitcoin Cash and Bitcoin Gold and B2X that we use it as an altcoin, but do we still need other altcoins? as i knew in the forum on the altcoin section there are much announcement about new altcoins almost everyday. do we still need that altcoins?

That may be possible even if bitcoin has been into constant crashes over the past three months to start the year. Just like last year, it went so many ups and downs before it finally skyrocketed to 20,000 before the year ends and i believe that it will gonna happen again this year.

Mind you, the law of crypto currency trading is to sell and hold your capital once you like your current profit. Meanwhile, the capital kept and hold is meant for another buying opportunity.
Its not everyone that panic sell.

Why is the world economy is sliding down, a bit reminder to  2008 when the world economy is in freefall, The shock waves from the collapse of Lehman Brothers maybe on of the main factors.. The economic indicators - trade, industrial production, unemployment - are comparable to the early stages of the Great Depression in the early 1930s.
My point is, how bitcoin could take place to helps the Economics rise again or it would be an additional threat to economy stabilty ??

For sure !  :p
https://99bitcoins.com/obituary-stats/

In 2018 i remain consistent to continue to hold my bitcoin, until the price actually moves up, because i am sure that by the middle of this year bitcoin will increase and become more valuable again.
I have great hopes in bitcoin, especially for my future and my family, so i keep investing and saving some of it to get a lot of profit in bitcoin when i later sell it for a high price.

Based on the news, bitcoin might hit $50000 by the end of 2018. Is this possible? If so, what are the reasons?

Patience in holding in trade is quite tiring, especially with the current market conditions are sluggish as it is today.
But there is no other choice, unless we want menwrima losses in trading. I think all traders do not want if you have to lose.

There's nothing wrong if you are going to take both of it. Just balance your time in each of it to avoid having conflict.
You can take all of your time in your job in the morning to afternoon. Then, if you have some time to do more another things, it is the time for you to trade.

This fluctuation of bitcoin price is a normal trend which we can view the market in a bloody marks. It's unstable but as we know we can see it's on a higher price just like the previous years happen. It will not take long in down trend however, bitcoin is not dead all of these can become better value in the market.

Start reading tutorials about trading and the technics of how to do so. Start watching video tutorials on how to use your favorite trading site and be sure you know the basic understanding of what is on trading or how to trade.

I truely think that now is the best time to buy bitcoin as an investment because it has a lesser value thereforeyou can buy it at lesser capital for your investment. For those who are investors already it is best to hold.

Most Indians are good with computers and technological issues, their programming skills are just some of the best in the market, hence their presence in ICO creation

This is at least something good. At least one Country is open to the good things that come with using Bitcoin. I guess because so many people send remittances back home they think it might be a more cost effective way to get money into the Philippines. We need more and more countries to be open to Bitcoin and make legislation that is welcoming to Bitcoiners in general, then if more and more people adopt it, then we might see a more stable price in the future and not a coin just manipulated by whales.

Choose an ICO > invest > hold > trade = your profit; or go to exchange > buy > hold > trade and so on; there's 2 basic ways.

Bitcoin is decentralized and because of the decentralization it is giving us freedom. Freedom of control of our money because there is no third party that will be there in our transactions.

It's tragic that people will not buy bitcoin. Of course the bitcoin will get worse.
But I still believe that it's all just temporary. Society can not escape the sophisticated crypto currency.

Yes there is some payable books that you can read but I don't think they are worth the money to spent just for learning in trading. Nowadays almost all of you want to know about things is in the internet, you just have to know how to make researches.
Sir @DarkSecretes is right ! There are many tips and guides here in the forum just kindly use the search button and there are also a lots of videos on youtube teaching you how to start on trading