at least the instance is up and running again.
But not THAT good..

@heluecht do you have any suggestions for me?

Since months, the database time for the Network page is unusual high as well:
Datenbank: 8.827/0, Netzwerk: 0, Darstellung: 0.07, Sitzung: 0, I/O: 0, Sonstiges: 0.32, Gesamt: 9.22 Class-Init: 0.012, Boot: 0.005, Init: 0, Inhalt: 9.205, Sonstiges: 0.002, Gesamt: 9.224

At first, I thought it's because of some missing optimizations. But I'm now sure that there's something wrong in the database ...