Doesn't work after changing graphic driver

Hi there
I use zorin 12 because of my old computer.
The resolution became bad. So, I decided to change driver. I tried to change as guide lines in this website. I went to settings and additional driver and selected nvidia driver instead of nouvena (the open source driver, I don’t remember the name good).
Then, zorin wanted to restart and I restarted. But when wanted to start again and show desktop, it doesn’t work.
Who can help me? It is an urgent problem.

Try Ctrl+Alt+F3. Then in the terminal try sudo ubuntu-drivers autoinstall.