Please explain

So I feel like this is a really dumb question but can someone explain sex a little better. I mean, I know the basics (penis in vagina) but honestly that’s about it. A few specific questions I have are: is it common to have pain after sex? How do you make sure your SO is pleasured? Is it okay to have issues the first time/ask your SO questions the first time? Around what age is it normal to lose your virginity? Is it awkward to have sex for the first time with someone? Should I be worried about being naked in front of someone? Will my SO judge my body?