Yeah, don’t do that.
Contabo have really, really bad images, so preferably you should change provider.
If that’s not possible, start with a clean image without Webmin preinstalled, and following the installation instructions.
These errors should not appear then.
If you have “much” extra time and want to learn, you can try the manual installation on that page and reading docs for that, only to learn more about your box and virtualmin setups if you want , but after that start better again with clean new one.
ONly pointing out while yes simple, start clean, but leraning path could be helpfull to do this better at a early starting point and not wait till your box is in production fase. because you write you’re no professional, by doings things by hand and also doing things wrong professionals started…
For own box, and not to much heavy sites Contabo is OK if you learn yourself , if for custommers so not your own then i don’t know.
Take care to get clean ip’s that are not on blacklists to be sure is waht you have to check at every hoster!