But today I register this forum because I need to know some answer about cryptocurrency and trading.
You still can see the answers even you don't register, can't you? Except if you want to ask questions, you don't need to register. However, it is a good decision to register and join the discussion. I really hope that you can gain more knowledge and brings something good to the forum. So, welcome buddy to the forum. 
I always follow trading, mining and bitcoin discussions section because these section give us good information and it's very useful for newbie.
Actually not only those sections have good information. There are many other sections that you need to visit. I also suggest you visit meta, you can see many things about this forum there. As you are a member of this forum now, it is better to know the rules, history, or even updates related to bitcointalk forum.