Backend: text only. Failed to load load-styles.php

Hi everyone,
so I’ve finally registered because I’ve encountered a problem I can’t resolve on my own. Please help me if you can!

This is the problem:
(The main problem being that I am not really a computer expert so please be patient with me):
My backend is text-only and there’s nothing I can do about it.

This is the information I have gathered so far:

load-styles.php?c=0&dir=ltr&load%5Bchunk_0%5D=dashicons,admin-bar,site-health,common,forms,admin-menu,dashboard,list-tables,edit,revisions,media,themes,about,nav-menus,wp-poi&load%5Bchunk_1%5D=nter,widgets,site-icon,l10n,buttons,wp-auth-check,media-views,wp-color-picker&ver=5.8.1:1 Failed to load resource: the server responded with a status of 404 ()
jquery-migrate.min.js?ver=3.3.2:2 JQMIGRATE: Migrate is installed, version 3.3.2
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DevTools failed to load source map: Could not load content for chrome-extension://fheoggkfdfchfphceeifdbepaooicaho/sourceMap/chrome/content.map: HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME
load-styles.php:1 Failed to load resource: the server responded with a status of 404 ()

What I’ve tried so far:
I have purged the caches and tried to open the backend in the most recent versions of Chrome and Firefox – with the exact same results.
Also, I have eliminated WP Cerber via ftp by deleting the WP Cerber folder.

How (I think) it happened:
So what I wanted to do is implement 2FA for my backend login with the help of Google Authenticator. This, for some reason, didn’t work. So I stumbled upon the information that if you remove the plug-in that you used (WP Cerber in my case), you can at least log in again. I was actually able to log in after that but the backend has been messed up ever since.

Thanks in advance for any suggestions!