How to fix anterior pelvic tilt?

Hey what is the real way to fix anterior pelvic tilt and back arch? My posture is bad and I need to fix that. I see videos talking about exercises I should do, and people tell me to always have a straight back, then I see a video that says holding a straight back will not help and it is bad, also see people say that exercising abs and glutes and stretching thighs and lower back muscles won’t help… what should I really do? I’ve went to a physiotherapist and he only said that I should strengthen my core. And I can fix my back at this age (15M) but when I get opder I may not get to fix it. So again, what should I do?