Hi... Why not if you are serious, patient and persistent... At school usually the children learn more than one subject during the day...

It depends on your capacity. If you think, you can do it, it is wonderful for you then. If you feel that it is hard for you, they try them one by one.

Well, it depends. In my opinion, if you are trying to pick up your first foreign language (yes, the very first one), I think it would be good if you could focus on that one first. Why is that so, you might ask? Well, I personally think that learning the first foreign language is tough as this is a process where you learn to get used to flip-flop'ing between the foreign language and your main tongue. However, if you already have a few foreign languages under your belt, then I suggest picking up languages of the similar linguistic roots or linguistically similar (it can be quite effective in terms of the amount of time and effort spent). For instance, picking up a few romanic languages together (Portuguese & Spainish, maybe?) might be good? Just my two cents worth. Hope it helps~

you must concentrate in one laguage to be a native in it then think in another one after you finish learning the first.

i prefer to learn one foreign language at a time.because every language has its own character like pronunciation and basic grammer, you may be confused when you learn mutiple once. so my advice is learn one foreign language once,when you reach a senior level then learn another at the same time.