Hey Basil,
thanks for your input. The key functionality is to auto-generate custom user-websites in subdirectories and wordpress multisite seemed great for the purpose of auto generating websites and the vast ocean of plugins to enable the users to use the features they need.
The wordpress single site is working just fine. The issue is really the routing to the subdirectories.
@francislavoie gave me the tip to look into checking out the nginx setting file and try to convert the settings from there.
see: NGINX Wordpress Subdirectories config
However, this is still a closed book to me, honestly.
Honestly, I’d love to take on @Whitestrake on his offer to help and translate the rewrite rules to the caddyfile 
Whitestrake offering to translate .htaccess to caddyfile
I’d be tremendously thankful ^_^"
@basil btw. really awesome animation when opening you website, bro 