French language Q&A Forum

Selon moi j'étudie depuis 2 mois en France = I have been studying in France for 2 months

J'ai étudié pendant 2 mois en France = I have studied in France for 2 months.

Est-ce que c'est faux pourriez-vous m'aider 

Why is "c'est bon" used here instead of "elle est bonne", when it's expressing opinion over something specific that you know the gender of already? 

I see that some verbs that take de or à and the infinitive drop the preposition when an object follows the verb.  As an example, choisir de drops the preposition when referring to an object as follows:

Je choisis de partir

Je choisis la cérise

As opposed to rêver that keeps its preposition in both cases:

Je rêve de partir

Je rêve du paradis

Is there a rule for this?

I  achieved 100 % in A1 level, then I achieved 100 % in A2 level and then in B1 level. But when I started working on B2 level I found out that my A1 and A2 are not 100% any more. Why? Is it normal practice or something went wrong?