How do I manage acne?

Now that I'm older, I don't get acne like I did during puberty.

This comes up every now and then when I'm on my period or in bad condition or tired.

But maybe it's because I don't take good care of my acne or because of my age?

It doesn't get better quickly and it seems to be leaving scars and pigmentation.

How to manage acne in the early stages when acne appears

I really really really want to get rid of it without leaving a scar.

Please tell me how to manage acne and prevent pigmentation.