after my VPS was down and at the next day I checked the VPS: it was online. Then I tried to visit my site but it keeps a white site. No errors or any letter/number shown. I thought it's just a simple problem and restarted Apache. It was still a white site. After I tried to access my adminpanel for my website I've got a white site too. No php errors, no errors logged or reported by Apache. Also my website files (index.php etc in /var/www) were healthy. I was so sure that Citynethost destroyed my VPS and told the support they need to fix it because they broke it within the downtime. They told me that they didn't destroyed the VPS but I staid with my opinion and told Khaled again and again that they damaged it and that they need to solve the problem, without any fees/costs for me. Khaled was very nice and said that I should check config files, logfiles and rebuild/reinstall otherwise Apache. None of his suggestion helped me and he can't believe it but then he checked it by himself via root access. It was not working and, after a lot of hours, he didn't find any problem. We were both idealess and he told me that he will search a backup for my VPS. He got one from yesterday (before it happened) and he could have applied it but I wasn't very happy about that. My idea was to backup mysql databases and /var/www and then rebuild the VPS. Khaled asked me if PMA (PHPMyAdmin) does work and I said I do not tried it. The first error appeared: PMA told me that it can't load mysqli. I did a reinstall of my php software (removed all configs via --purge and then reinstalled php and phpmyadmin) and it's working fine now!
At the end of the story I can say that Khaled looked for the problem and it wasn't their fault. I don't know why my php got destroyed but it doesn't look like their fault. Me and him didn't saw a such happening before and it must be happened through a bad mix of wrong time with wrong happenings. Maybe the Dotdeb-Mirrors created a incompatibly but I do not know the problem for sure.