ANSWER:

This is not kufr!

It’s sinful to look at non mahram women like this whether below or above 18 years of age as Allah has ordered you to lower your gaze!

I’ve read that in islam there is no restriction of age for intercourse,puberty is enough, but where i live there’s this idea of people over 18 shouldn’t be with those under 18,and i’ve grown up with this,so now i’m struggling,for example if i see a female under 18 i may feel bad(because of people around)and stop looking at her even though she’s lawful to marry, is this Kufr?