Ah, it's common for elderly dogs to go through patches of not wanting to eat. Sometimes, it is just a case of feeling a little off colour but not anything life threatening. It's hard not to worry though and think the worst when they are old.

In the UK, we have metatone tonic for people to perk you up and get back your appetite when run down or after illness and I find this also works well for dogs and other animals as a pick me up. My sister uses it on her cavies. It is just a blend of vitamins and minerals so nothing that will harm him. Worth seeing if they sell anything like that in Germany.

Hopefully, he was just feeling a little run down.