Occ and the user privileges


I am using owncloud in version 9.1.8 with SQLite as database on a Vserver with ubuntu 16.04 using Plesk 12.8 as admin interface.
I have created a specific subdomain to individually run owncloud on this subdomain. It all works nicely since years. But now I want to upgrade to owncloud 10 and it does not work since I have some user settings to manipulate using occ console command.
And this is the problem. whan calling occ or sh occ on the console I do get the following error:

occ: 2: occ: cannot open ?php: No such file
occ: 3: occ: /aquota.group: Permission denied
occ: 4: occ: Syntax error: "(" unexpected

I guess it is an issue with user privileges. All files in that domain are group “psaserv” and user “onkinet”. I am using php 7.0.18 (by OS provider) and I guess this is a problem as well.
In order to get prepared for OC10 I want to migrate to MYSQL and switch to PHP 7.2.9 (fastCGI) after upgrade to OC 10 (since OC 9 does not support PHP 7.2).

Any tips on how to get occ to work on my server?

Best regards

Database Migration works in theory but is problematic in reality.

I would recommend a new DB in MYSQL.

Also PHP 7.2 is not yet fully supported by ownCloud, so I would stick to 7.0.