Bunnies back nails are thicker than their front nails. They are pretty flat from the side though.
The 90 degree turn sounds like really overgrown nails. It’d be good if you could upload a picture!
It’s important to cut their nails or they’ll put pressure on parts of the feet where they shouldn’t and that can lead to f ex sore hocks. It’s good if you can be two people, one that holds the bun and one that does the cutting. Unless the nails are all black it can be useful to put a flashlight behind them so you can see where the quick ends. Styptic powder is good if you happen to cut into the quick, or you can press the cut nail into a soft bar of soap to stop bleeding.
If the nails are black so you can’t see the quick it might be better to have a vet tech or a vet do it. If they deem it necessary they can anestetize the bunny and cut the nails and burn the quicks (the quick grows out as the nail grows out) so there’s no bleeding even if they have to cut off a lot.
How silly of the previous owner to tell you bunnies don’t need nail-clipping!