I really need to find Grav pros. I tried to find some on fiverr, but did not succeed - in fact I threw away some decent money for nothing.
Where could I find a real pro whom I could hire in order to get my sites and themes fixed? Do you have any ideas?
Usually in #jobs-listing on Discord, or on here, if you post about the type of work and specifics about contracts. Fiverr, and all other $1-50 sites, yields more work in my experience. The quality of the work is low and it’s usually a hassle I’d have paid to do without.
“Pros”, in the sense of professionals, are rarer in this space. Because of market-shares and name-recognition, the ones you’ll find specialize in multiple CMS’, and web-development broadly. What’s worked in the past, when people need someone with Grav-expertise, is either post a specific job as mentioned, or gone to Trilby.media which are now the people behind Grav.
This is all to say, expertise does not come cheap, as your experience with Fiverr testifies to.
I’m available, DM’d you 
Thank you very much for your input! 
As @hughbris already contacted me, I will refrain from posting anything official right now for the time being.