in hollywood movies..in the sex scenes...are they actually having sex?

No, they're not actually having sex. They actually kiss, but MOST don't. It's common practice to have body suits on or do trickery with the cameras. In porn, they DEFINITELY have sex every time.

It would be unethical for anyone to offer an actor a job but on the condition that they would have sex with someone on camera. It would be illegal for anybody to propose it.
Of course actors need to be comfortable simulating sex but a film studio isn't the kind of place you'd actually want to do it.
It takes a whole day or longer to shoot these scenes, and each different camera angle usually requires everybody but the camera man and the lighting technician go have a cup of tea for forty five minutes.
It's all acting, and very temporary.

if they are then its called a porno

Fuck Ya They're Boneing

children you have know idea what man dose to himself, in truth yes thet do sometimes
have sex in some holywood movies they edit the more exsplicit scenes, all of that will stop soon as my novel comes out

freaky shit