score:4
The numbers are on little (wooden) panels that can be pushed in a (wooden) rack. In your case both panels and rack have the same colour a the wall, so they are a bit difficult to see.
The numbers give the songs to sing during the service. The red numbers give the verses to sing.
On the denomination: First I thought it is a Catholic Church (esp. because the seats in the sanctuary), but the numbers given lead to songs in the Catholic song book "Gotteslob" (then used 1975 edition) not fitting on a burial. The songs of the protestant "Evangelisches Gesangbuch" fit better. So probably it was a protestant (near Oldenburg: lutheran) service, but I may be mistaken.