How to change WP theme through phpMyAdmin
If you have a bad theme, You can discontinue use of the theme, find an alternative theme, try to re-install if see if that fixes the issue, or contact the developer/publisher of the theme for help to see if they have a fix or patch for the theme.
You will need to log into phpMyAdmin, if you are not sure how to, you can get all the info right from the panel.
How to Log in to phpMyAdmin
Then you will see the database in the upper left side
Select the database for your site
Now you will see the info for that database. What you are looking for contains “options“, the prefix can change, select the options.
Then click the browse
You can display more rows if you would like. Next to the Show you can see I have set it to display more rows to make it easier. Now you will see template and stylesheet:
You will click the Pencil (this is the edit button) next to next to the entry to modify it. The edit page:
Type in the new theme or default theme and click the GO to Save. You will need to do this for both the template and stylesheet.