My oldest friend´s name is Luan. (I don´t see anything wrong with the other version, but it´s just my choice of words here)
Our friendship didn't begin/start at any specific event, (a sentence with a negative statement asks a "any" afterwards)
I believe that this friendship was natural. On the playground we stayed together at the same time and the same local and We had another
*other friends **as well, all of the same classroom.
Another means "um outra/uma outra.
Other friends too...generally "too" is used at the end of a sentence, either you would end the sentence at "too" and go on with "all the same classroom" or replace with some equivalent to it. I have chosen "as well''.
As for the preposition "to", in "another friends to", certainly was a typographic error. At least, it´s my educated guess.
We were together nearly/almost every day at school and on the
weekends we played RPG with our friends, we were a group of 7 kids, some were (actually) older than us/than that.
At those times we drank soda and ate some types of fast foods.
(at that moment has a certain ring of a "little while" to me, not much, not a full weekend day. But then, it´s just my opinion here)
I went to university , but Luan decided to study more to pass at Unicamp. Today I [was--?] I am graduated and am working.
Recently Luan succeeded at passing the exam to Unicamp, after 4 years without we seeing one another, since then.
Now/some time ago we met again to celebrate. We called all our friends.
And we (now/since then) meet two times a month, we are
to play RPG on the
weekends with our old friends.
"Oldest" and "friends" is a very rare construction, one could say "These two are the oldest friends I have" for stance, but to say so about a group would be very rare event.
I will leave the fine-tuning to the advanced guys, anyway this is something to go by. Okay?
Hope it helps.