autotutorial

From your email search on spam or principal with the term Cloudflare ftp.
I could not trace back to your domain.
Usually you have to use a ftp client with passive mode. (it is important if you are behind NAT).
Ask your hosting for more information.

Warning: require(/home/nikola797992/public_html/jumpmanual.org/wp-includes/class-wp-user-request.php): failed to open stream: No such file or directory in /home/nikola797992/public_html/jumpmanual.org/wp-settings.php on line 166

This file /home/nikola797992/public_html/jumpmanual.org/wp-settings.php for some reason it cannot find this file, the problem is due to missing files, loader that does not launch this file or owner problems and / or folder and file permissions.
In your case it is the first option, the partial update. /home/nikola797992/public_html/jumpmanual.org/wp-includes/class-wp-user-request.php

Change your https://en.m.wikipedia.org/wiki/Grave_accent for '
define('WP_MEMORY_LIMIT','256M');
also make sure you don’t use all the images in a single folder.
https://wordpress.org/support/topic/media-folders-on-the-server/

From wordpress 5.3 set in the core Gutenberg 6.6, if you use the Gutenberg plugin you must also upgrade to 6.6 or later.
Switch to the default theme one of twenty*, disable all plugins except Guterbeng (if it is installed as a plugin).
If you don’t solve the problem here is the guide on how to trace javascript errors.
https://wordpress.org/support/topic/read-this-first-wordpress-5-3-master-list/#post-12124044

there are some plugins (firewalls) that use a php script even with the plugin disabled, did you also update the database (wp-admin/upgrade.php)?
Use the Classic editor

If you want to delete index.php you need to enable url rewriting and it depends on your server (mod_rewrite for Apache) Pretty Permalink

can you temporarily add this code before of foreach? Add post
I would like to analyze the output

if(!function_exists('var_x_error_log')) {
if(!is_array($this->supports) && !is_object($this->supports)){
function var_x_error_log( $objectauto=null){
ob_start(); // start buffer capture
var_dump($objectauto); // dump the value
$contentsauto = ob_get_contents(); // put the buffer into a variable
ob_end_clean(); // end capture
error_log( $contentsauto."\n",3,dirname(__FILE__).'/test.log'); // log contents of the result of var_dump( $objectauto)
}
var_x_error_log($this->supports);
}
}

This script create http://yourdomain.com/wp-includes/test.log
it is enough for me to post only the first incorrect result, then delete test.log and this script.