[Realism]

1) Is Japanese a hard language to learn from someone who live in Europe?

No it's not.....if you learn Kanji first then it's not. So I advise you to learn Kanji first.

2) What is the average time to learn Japanese to have the "level" to speak "easily" in nearly all situations (like on the forum or in conversation)

1-2 years if you immerse yourself into the language. You know...like daily immersion where you listen to and read Japanese all the time.

3) What about the pronounciation of this language?

Easy

4) About the difficulty, how do you compare the French and the Japanese language?

Hard to say. I don't speak French. But every language has its quirks.

Thanks a lot! Sorry if my english is sometimes wrong ><"