Good news is we now know you are using the Froxlor control panel to manage your Let's Encrypt certs.
Bad news is we rarely see problems with that on this community. I personally know nothing about it and their docs were not helpful. In fact, their docs section on "SSL" was empty.
Maybe another volunteer will know more about Froxlor. Or, try contacting the authors of that directly. Their github and main websites are below. Or, contact your hosting provider if they provided Froxlor as part of their package.
I don't know. Sometimes control panels want to manage the entire server config and making manual changes with another client can make things worse. Other times it can work fine. I personally don't know Froxlor enough to say.
That's probably a better question for Froxlor experts / users on their github or website.
Nonetheless, they should be the persons who can provide you with help on how to decently debug this issue. Does Froxlor log the output of acme.sh? If so, where? Et cetera. We don't have a clue
Froxlor is the front-end of acme.sh. It's kinda lame to throw your issue over the fence and say "It's not our problem!".. Acme.sh a tool used directly by Froxlor so Froxlor should provide enough support on how to handle this. Froxlor is handeling (or should) the renewals, Froxlor is handeling the webserver, Froxlor is doing everything, even if it's just delegating.
Adding on to Osiris comment, @steki refer back to your post #7. It shows the certs and server config files in Froxlor specific folders. They set up a custom configuration.
If you can show us the error issued by the Let's Encrypt servers we could maybe help. If there are any they should be in the Froxlor or acme.sh logs. But, errors can occur within either of those systems too. It might not have anything to do with Let's Encrypt specifically.
I don't see anything obviously wrong with the connection to your server. And, the Let's Debug test site sees it ok too.
If your hosting provider included Froxlor with your package they should be able to help.
[Sun Jun 19 18:39:15 CEST 2022] Renew: 'tools.artfil34.de'
[Sun Jun 19 18:39:15 CEST 2022] 'tools.artfil34.de' is not an issued domain, skip.
2 root@galerie-admin /etc/cron.d # ~/.acme.sh/acme.sh --renew -d wiki.galerie-admin.de --server letsencrypt
[Sun Jun 19 18:39:52 CEST 2022] Renew: 'wiki.galerie-admin.de'
[Sun Jun 19 18:39:52 CEST 2022] Renew to Le_API=https://acme-v02.api.letsencrypt.org/directory
[Sun Jun 19 18:39:53 CEST 2022] Using CA: https://acme-v02.api.letsencrypt.org/directory
[Sun Jun 19 18:39:53 CEST 2022] Creating domain key
[Sun Jun 19 18:39:54 CEST 2022] The domain key is here: /root/.acme.sh/wiki.galerie-admin.de/wiki.galerie-admin.de.key
[Sun Jun 19 18:39:54 CEST 2022] Single domain='wiki.galerie-admin.de'
[Sun Jun 19 18:39:54 CEST 2022] Getting domain auth token for each domain
[Sun Jun 19 18:39:56 CEST 2022] Getting webroot for domain='wiki.galerie-admin.de'
[Sun Jun 19 18:39:56 CEST 2022] Verifying: wiki.galerie-admin.de
[Sun Jun 19 18:39:57 CEST 2022] Pending, The CA is processing your order, please just wait. (1/30)
[Sun Jun 19 18:40:02 CEST 2022] Pending, The CA is processing your order, please just wait. (2/30)
[Sun Jun 19 18:40:05 CEST 2022] Pending, The CA is processing your order, please just wait. (3/30)
[Sun Jun 19 18:40:09 CEST 2022] Success
[Sun Jun 19 18:40:09 CEST 2022] Verify finished, start to sign.
[Sun Jun 19 18:40:09 CEST 2022] Lets finalize the order.
[Sun Jun 19 18:40:09 CEST 2022] Le_OrderFinalize='https://acme-v02.api.letsencrypt.org/acme/finalize/97618304/99200566676'
[Sun Jun 19 18:40:11 CEST 2022] Downloading cert.
[Sun Jun 19 18:40:11 CEST 2022] Le_LinkCert='https://acme-v02.api.letsencrypt.org/acme/cert/0374461ff9ebadbbb3467a8aeb8ad6923870'
[Sun Jun 19 18:40:12 CEST 2022] Cert success.