Can't complete the login into my MacBook Pro admin account

when I try to login to my Macbook Pro admin account it accepts my password, but I get a line underneath like it's downloading/installing but never completes. It stops at the middle and i get a black screen. How can I fix it?

And even when I try to login to the guest user it logs me in and open safari immediately without any toolbar and the background is black.

I don't know what's the current operating system, but I think it's the latest one or the one before it.