Could anyone recommend me a manga or a webtoon about a strong female character (she knows ...

I already read those but thanks (⌒▽⌒)

Sorry it's not a school life (nor really romance so far) but "May I Ask for One Final Thing" is really good. The female lead is one of the most badass characters I've ever seen.

that one is really cute
http://www.mangago.me/read-manga/seishun_otome_banchou/
dunno how this will turn out but its good
http://www.mangago.me/read-manga/raise_wa_tanin_ga_ii/
the girl is a lil fool, but strong minded and not weak
http://www.mangago.me/read-manga/you_re_so_cool/

These don't have much romance but they are really good :
Hibiki: Shōsetsuka ni Naru Hōhō
Act Age
Delivery Knight
Zero Game
Hoshizora No Karasu
Sachiiro no one room
Yamase wa doko e itta?
Gokigenyou koharu-san
Aruitou
Kusuriya no Hitorigoto

Thank you very much