installation problem: mariadb service does not recognize that the server has been started

We can not install mariadb or any other mysql version. We tried >20 times to install mariadb with a clear debian 9 img from our webhoster zap-hosting.com. It works fine with debian 8.
Error description:
Problem: since Sunday 28.10.2018 afternoon

• mysql socket not found and could not be started
• Generally different service crashed (may be a other problem sincce we installed new packages)
  mysql still does not work->
  Overview:
• with debian 8 the installation goes through
• when installing debian 9 the error message (> 20 times tried with zap-hosting Debian 9 img without other components to install) we get this error:
• https://gyazo.com/5f6830907b3a97e7f0810b151a7eb4d6
• try to start: Can not connect to the local MySQL server via the socket '/var/run/mysqld/mysqld.sock' (2).
• the socket is not there either
• Updated repository or inserted new source
  mariadb / mysql debian 9 Source tried -> failed

Our Linux version is:
Linux 12505 4.15.18-1-pve # 1 SMP PVE 4.15.18-17 (Mon, Jul 30, 2018 12:53:35 +0200) x86_64
or.
Linux version 4.15.18-1-pve (build @ pve) (gcc version 6.3.0 20170516 (Debian 6.3.0-18 + deb9u1)) # 1 SMP PVE 4.15.18-17 (Mon, 30 Jul 2018 12:53 : 35 +0200)