The people who hasve crazy numbers in their streaks marks usually have in common a great quality in their writings.

the words "in common" can be removed, since the subject of the sentence is already talking about "the people".

I would like to become fluent in English and be a great writer in the future, but it's being pretty painful now at the beginning of the journey.

I write a lot on paper (crazy a lot) in English, but doing it in public is another history.

The word "Story" should be used instead of "history". The phrase usually goes something like this "A, but B is a whole another story". I think you understand the idea of the phrase already.

Besides, here is a great community.

Actually, this is the best I have been in my life (8 years since I have access to Internet).

Commitment is required here to be successful, as it is with all good things in life.

I'm really glad to be here, and I hope I can do my best to contribute withto this good cause.

What do you mean by this sentence?
If you want to write a lot on this site to improve your English, then a more natural phrase would be "I hope I can do my best to achieve this goal"
If you are talking specifically about using this site to help others a lot, a more natural phrase could be "I hope I can do my best to contribute to this community"

"a good cause" is normally used when someone is referring to a charity or some type of charitable action

The people who has crazy numbers in their streaks marks usually have something (one thing) in common a: great quality in their writings.

I would like to become fluent English and be a greatbetter writer in the future but it's beingright now it's pretty painful now at the beginning of the journey.

I don't even know yet how to effectively manage feedback effectivelys yet.

I write a lot on paper (crazy a lomount) in English, but doing it in public is another hi different story.

"Crazy amount" is the best way to say this as we don't usually pair it with 'a lot'
"...is a different story" because you are talking about what would happen if you're comparing it to your own experience of doing it in private vs. doing it in public.

Besides, hereit is a great community here.

Usually it is common to use 'here' at the end of sentence for this phrase.

Actually the best I have ever been in my life (8 years since I have access to Internet).

I'm really glad to be here, hope I can do my best to contribute with thisfor a good cause.