if I were you Isabel, I would...
- Change to the Boost theme and then make sure your site works correctly.
- Remove the Adaptable theme from your site using the UNINSTALL option in the Plugin overview page
Once the above has been done you can Upgrade Moodle to the latest version of 3.6+ providing that you have made backups.
Then when all is working correctly you can install the newest version of Adaptable compatible with your Moodle site.
Hope this helps?