Being a native does not make you a grand wizard in that language. You become adept in the language to which you devote yourself. It's usually, naturally your native language, but there are no proclamations that entail this to always be true. I've studied English my whole life, I'm 28 now, to the point of ruining my native language proficiency. When I write in my native language, I constantly make severe grammar mistakes and my vocabulary is null.

English is one of the most, perhaps [i]the[/i] most synonym heavy language in the world, so don't beat yourself up if you forget that there are between three and perhaps a dozen synonyms for any given word. Thesauruses are good, reading the [i]proper material[/i] is better. 

Learning basic, English grammar is easy. The intermediate levels are not that difficult either. I've been thinking about creating a grammar guide for the forum, which has all the basic stuff in a clear and concise format.