Hi im trying to find out which chapter negima Is the end of the anime Thx in advance.
As stated earlier, the end story-arc of the Negima! anime is not in the manga. Further, the Kyoto Arc was compressed down to just two episodes from three volumes of manga (though to be fair, some story elements from the Kyoto Arc where redone so that they wouldn't take place in Kyoto, and thus became pointless).
The timeline hasn't jumped (yet), if that's what you mean. Neither of the two anime (there are two) follow the real manga storyline, and the manga is far from finished. I'd highly recommend you read the manga from the beginning, as far as my oppinion goes, it's vastly superior to both anime.
does anyone know what chapter he becomes an adult?.
You can say he is still ten (although biologicaly he is probably eleven) in current story arc (in volume 21+)... Maybe you have seen some images of "16 year old Negi", but that's just a magic ilusion...
And about anime-manga...I think some differences are even in first episode of anime... I personaly hate Negima! anime because it is completely screwed up...:/ just like Love Hina anime... Akamatsu is sucha a great mangaka...I really don't understand why they always change his work when they make an anime...:/