make it up = pretend that something is true

Let's make it up. < Let's just pretend - or do something without a plan. (Let's make it up as we go.). Similar: Let's make up. < Let's not figiht anymore and be friends. (Let's kiss and make up.) ~ I wasn't sure which one you meant.

i never made up with girls, only made out :P

'make up' is often used to mean "to make up a story", i.e. to create a lie....

what's the context? IF we see this in english we would say "Make what up"?