Error after change to php 8.0

I updated my Concrete5 Version to 9.1.3. Afterwards I changed the php from 7.4 to 8.0. Now the Website won’t load and I only see error messages. I have no idea what to do and how to fix it. I attached a screenshot of the error and I hope somebody can take a look and help me out. (I temporarily returned to php 7.4. but have to change it until the end of the month.)
Thank you in advance.

your printscreen speaks about package; maybe some of them are not well updated or do not accept php8, try disabling them (all) and change php version, to see if the problem persists; if no, it’s a package, try to activate them one by one, then you’ll find the one which is causing the problem, maybe you may just update it - or forget it

Hi @Lebensenergie - on your new version of PHP, do you have warnings displaying as exceptions? It looks like you might, so you would want to change that in your php.ini

I deinstalled every add on and even the template I was currently using, as it is not updated to Version 9 yet. Unfortunately the problem persisted.