You should be able to log normally from that prompt. If it puts you at a terminal instead of starting your normal GUI, you should be able to type startx to get back to a normal system. I'm sure this isn't what you're looking for, but I'm not experienced enough to guess what's going wrong; I'm just trying to let you use your system while you wait for a more advanced user to help.
What did You do before? Was there an Update? Did You installed something? Uninstalled something? Did You an autoremove Command? A bit more Informations would be nice.
thanks for your attention, but, i searched in other forums and i found the solution! for the ones that came here for information, just log in in the prompt and type sudo systemctl start gdm, and log in again. in the terminal, type sudo apt-get install --reinstall gdm, and all will be working again
and again, thanks for your attention, i love the linux community
I think it should be gdm3 not just gdm?