As numerous other customers have already written, ...

As numerous other customers have already written, it is stated that an attempt was made to deliver, although someone was definitely at home.

Also that the address was not found and the delivery was sent back to the sender was already there.

My personal impression is that they try to do something like this with extremely untrained staff.

For my part, I will lodge a complaint with the sender. I don't know if it will do anything. DPD is probably too cheap and you don't change there.