From admin page, I can't do anything

I had to reinstall my wordpress for some reason, and have the site back up, but now a lot of the links lead to the same page, and from the admin page, for instance, if I try to reset the permalinks so my custom links within pages work again, I get thrown out to the login page, and it won’t let me log in. If I replace the .htacess file with an old one, I can log in again, but then I’m back where I started with no changed permalinks.

I can’t get into my posts page either! It throws me out into the signon screen!!

I have no idea what to do! I can’ export the site either…