A far from stupid girl.

I was a stupid girl. <full stop required> I do not know everything about English. <Must have a space, or 2 after a full stop> But I love English and I want to learn English well. Who can help me to learn English well?

If you want to write English well, concentrate on those capital letters even if some refuse to.
The missing space, or 2 spaces, after a full stop is also a common mistake here.
The English language always has a capital letter on English.

In what you wrote it would seem rather than begin a sentence with "but" you could also go with;
I do not know everything about English but I love English and I want to learn English well.

Many English speakers over use commas & might use
I do not know everything about English, but I love English and I want to learn English well.

Your use of "learn English well" is good. The difference between adjective "good" & adverb "well" escapes many native English speakers.

I suspect that with your already good English, you wanted answers rather than corrections.
Books, movies, podcasts, news, there are likely lots of language partners here: there is nothing like meeting in person though.
Maybe try options. Try on line chats in English, voice chats, skype, &c. See what works for you.
Sites like this & chats with native English speakers are getting easier, as more English speakers join.
You have obviously done a lot of study to get where you are, keep it up.

a stupid girl

I was a stupid girl, i do not know everything about english.But i love english and i want to learn english well. Who can help me to learn english.

Congratulations Shelly!

Everything is perfect, except for capitalization!  And since "texting" on cell phones has become popular, most young people in America no longer use capitalization, either. 

So, if you prefer to not look like an old lady, then you shouldn't capitalize either "I" (when used alone to denote oneself), or "English."  Yes, we older English speakers capitalize more words than almost any other language.  We capitalize so much, we even capitalize the names of languages!!