"Schäfchengrüsse" by Axel Scheffler. Scheffler is a German artist who has lived in England since the 1980s, where he is a well-known illustrator of children's books.
The bottom stamp we've seen before. I went to look for the one on the top on Deutsche Post website, and I can find a picture of the stamp, but only in the section for buying "a variety of stamps" all worth 55 eurocent, and with no info about the stamp. Thank you, Deutsche Post website, for being of no use whatsoever.