Do females like fast or slow sex.

There's a lot of variables. The size and shape of a penis and vagina, how wet a girl is and how hard a guy is, how much stamina you both have, mood and plain personal preference all matter. The best thing to do if you're having sex with someone and you don't know what they like is whatever you like (so long as it's relatively vanilla). Keep asking "is this good?", "do you like that?", "is there anything you want me to do?" etc., then do it if it's something you like too. That way you both get things that you want.