Messed plugin_settings

I was installing a theme plugin and I decided to disable the default theme. After that I got a 500 error and I managed to reenter the backend with some changes on the db (nothing worked) and by deleting the bad theme. Now I don’t have a theme, and I cannot set plugins from backend. I am actually trying to install a new teme and hope to get the default fixed (I copied the clean folder from the zip).
Where can I find the correct settings of plugins?
Thank you for any suggestion.