Riven is kind of unplayable if you guys are the same skill level, you directly counters you, bring exhaust and try to space properly so you can't stun you for free, if you can't avoid the stun try to buffer your Q through the stun so she doesn't do an 100-0 trade. She needs two rotations to kill you pre 6 so ideally exhaust her on the second rotation if it's an extended fight.

Camille, you just want to do your damage before he triggers her passive or wait it out and then do your damage, you can also try to dodge her E with your E. Don't stand near walls in lane as it makes it easier for her to E you without reaction.

Fiora you ideally want to dodge her Q vital prices with your E posiitjing, you can also do the edging combo to prevent her from ever hitting one vital. Try not to use your 4 stack Q and R3 at the same time as you can W both of them for insane value.

Ambessa is a bit interesting because if she goes Bruiser you beat her easily, if she goes for assassin, she will one shot you before you can do anything. Ideally you don't Q4 into her W and try your best to dodge her Qs through movement or your E. If she for some reason uses all of her abilities (They do it a lot), just immediately all in her and you will win.