Slow backend - Plesk, WP, Divi Theme (+ Builder), WooCommerce

Dear crowd,
I'm using webhosting service from www.webhoster.ag /.de which provides Plesk administration.

Recently I installed following:
- Wordpress (which was available in Plesk)
- Within Wordpress I installed/added "DIVI theme + builder" as well as "WooCommerce"

Issue:
- Since I added WooCommerce it's taking a lot of time to load WP dashboard and navigate within. Also Plesk is a little bit slower, but WP dashboard is like "waiting up to 10 seconds until another site opens when moving within WP dashboard's menu"
- The website load is also very slow
- When installing another plug-ins like WP Multi-Language it's getting even slower with reaction time of WB dashboard of 15-20 seconds

Notes:
- Everything was freshly installed, so almost no historical data or settings of the server
- Also Wordpress, DIVI and WooCommerce are completely empty / default
- I did some improvement changes, e.g. activating APACHE/NGINX
- max_input_vars=5000
- memory_limit=1024M

Questions:
- What could cause the issue / what could resolve the issue?
- Who could support me with general settings within PLESK?
- Is it a problem if I have a root directory where I added folders and where I defined, that for each of my domains a separate folder is the root directory, e.g.
- /root directory/website1/ -> this is root directory for www.website1.com
- /root directory/website 2/ -> this is root directory for www.website2.com
Reason why I'm asking: I can see, that WP placed folder within /root directory/ e.g. .wp-cli and wp-toolkit

Thanks,
Markus