pls. have a look at "/usr/local/psa/var/modules/letsencrypt/cli.ini.sample".
In addition, you might be interested, that the Let's encrypt "certbot" has additional options, which you are able to list with the "--help" - command for example:
renaming /usr/local/psa/var/modules/letsencrypt/cli.ini.sample to /usr/local/psa/var/modules/letsencrypt/cli.ini and commenting the test server entry did it, tnx.
One tip: you must delete the existing certificate and get a new one, only renewing doesnt seem to be enough.
@UFHH01 advice was spot on. I was able to just renew my certificates without deleting the existing ones. I just had to be sure my browser cache was deleted before browsing to the domain again. Before following the advice of @Linulex be sure to delete your browser cache as you shouldn't need to delete any certificates, the renewal process automatically does this.