Ever since caching strange warnings from other plugin + can’t deactivate

HI,

Via e-mail I got the message that most of my files had changed and it turned out they ” were cached’. Normally a good thing, but the result was that a certain plugin is no longer functioning and giving warnings.
That has never happened. I never had issues with this plugin, but the only change I did make to my website (after a tip from a designer) was to change from W3 Cache to WP Super Cache because W3 was unreliable. But now my theme and/or Easy Collage plugin ‘breaks’.
I have pages full of warning signs now (looks ridiculous) and no imaging. This is one of the warnings: Warning: getimagesize(https://www.thequeenssword.com/wp-content/uploads/2016/01/Scan-2016-1-14-0002-15.jpg): failed to open stream: HTTP request failed! HTTP/1.1 403 Forbidden in /home/thequeen/public_html/wp-content/plugins/easy-image-collage/helpers/layouts.php on line 212
(See how a whole article looks: https://www.thequeenssword.com/sola-busca-tarot-by-mayer/)

I tried to deactivate *your* plugin to solve the issue, since this has been the only change AND I had gotten the e-mail, but for some reason the Plugin now refuses to be deactivated.

“I get the message: Could not remove WP_CACHE define from /home/thequeen/public_html/wp-config.php. Please edit that file and remove the line containing the text ‘WP_CACHE’. Then refresh this page.”
first of all: Why can’t I simply deactivate via the plugin menu? Secondly: I have no idea how to do this and where.

When looking into the settings, or trying to I also have two other warnings:
1. Warning! Could not update /home/thequeen/public_html/wp-config.php! WPCACHEHOME must be set in config file.

2. Warning! /home/thequeen/public_html/wp-content/advanced-cache.php does not exist or cannot be updated.

I really can’t keep my site like this. It looks atrocious, publishers will start to comment, and I want to have it up and running again and at least be able to deactivate/delete WP Super Cache.

Please help me out (due to time differences I might respond later. I have been trying the whole evening to fix this and it is practically midnight… I am exhausted).

Best,
kalo
https://www.thequeenssword.com