I would like to improve my english and speal fluently, let's say correctly; but I think I misunderstood, I thought I can learn via this website; But it is a mess, I do not know how abd where to start. Maybe they don't teach english?
From what you have written, your English is quite good. As far as I know, this site does not teach you English in the way of a study course or a series of lessons. What it offers is you can post questions concerning English words or sentences for which you don't know the answer or correct usage, and someone may answer your question.
Ask an English teacher to recommend a book for improving your English suitable for your current level. You can also read story or other interesting books written in English and watch English language documentaries on TV (the English narrated in documentaries is usually spoken more slowly and clearly than in other TV programmes).