Is it correct to apply sunscreen every few hours?

I always get confused between mineral and chemical sunscreens. Also, how often should I apply them? And what is the right amount? Even though there is quite a lot of information available, I keep forgetting, haha. How often do you all reapply sunscreen? It’s really not easy to reapply sunscreen over makeup after putting it on in the morning. If I apply sunscreen and then pat on cushion foundation again, it feels like it makes my skin look too thick. Still, reapplying with a tone-up sunscreen seems to make it a bit better.