Our friendship goes back about 8 years ago. In the beginning, we were
not good friends. We were classmates. but When we were in grade 3 of high school
at grade 3, we went to camp, and there we got to know knew each other more. From
then until now, we had a good relationship with each othertogether. but There are
differences between us. I went to university, but he didn't go, and
recently, he got married. Naturally, our friendship is more less weaker than it was in the
past, but we are still good friends yet.

Good job, Saeed!

-Either "Our friendship goes back to about 8 years ago" or "Our friendship goes back about 8 years."

-Try not to start sentences with "but" or "and".

-I would say "When we were in our third year in high school," but if you say "grade 3," it should be "grade 3 of high school."

-A more natural way of saying "From then until now" is "Since then".

-"Yet" and "still" are only the same if they are in a sentence with a negative verb.

هنوز این فیلم را تمام نپاییده‌ام

"I have not watched the movie yet." OR "I still have not watched the movie."

دارد درس می‌خواند

"She/he is still studying."

غذا را تا هنوز گرم است بخور

"Eat the food while it is still warm."

My best friend

Our friendship goes back about 8 years ago. in the beginning we were
not good friends . we were classmates. but when we were in high school
at grade 3 , we went to camp and there we knew each other more. from
then until now , we had good relationship together(I think it should be "with each other". But I'm not sure!". But there are
some differences between us. i went to university but he didn't. and
recently he got married . naturally our friendship is more less than
past , but we are good friends yet.

I'm not a native speaker. so I'm not sure whether I corrected it completly or not!