I have made my account two days ago. And I just made only 5 posts.
I am giving the whole time to this forum and getting a lot of knowledge about cryptocurrencies world.
That is a good approach, to get yourself familiar with the forum. Take your time, read the rules, there is no need to rush into anything.
Should I choose a one topic like current affairs or only bitcoin or only altcoins discussion or should I post everything here.
Regarding your question, in my opinion it's best you write about the stuff that you are interested in, whether it's bitcoin, altcoins or something else. Don't feel pressured writing in some section about stuff that you don't care about as it will affect your post quality, whether you want it or not.
Since you are still new I would advise you to read this guide made by @tranthidung
Bitcointalk posting etiquette. It has a lot of good info and will set you on the right track from the beginning.