how can i add more than five stories stories to a building? i mean actual stories, not just stretch the existing ones with constrainfloorelevation.

im aware for frame rate issues that might occur, my pc can take it. help?

That's the game's limitation. Got nothing to do with whether a PC can take it or not.

There's been some workarounds using CFEs - check the Building forum - under the Create menu. If that's not something you want to do, then the only other solution is to have EA redesign this portion of the game engine differently for The Sims 4, if there's to be one, I mean.

my building doesn't even have five stories, it has 3 cause the other 2 are friezes. i wanna place a 3rd one on the roof, does that come closer to possible?

As long as you can place a floor tile, it counts as a storey/level. Max 5 above ground and 4 (?) below ground with the basement tool.
Which means you've maxed out your storey allotment with 3 storeys + 2 friezes.

Also, moving to the Building section, as your game does not appear to be broken.

As I can see you have 3 options

1: build fake floors with cfe
2: use ugly premade EA shells.
3: build basements below ground.

The thing is, a wall is a wall when you're above ground. Foundation, walls or friezes all add a floor.