It was hovering and in between it was very fast and hard to photograph. I'm not even sure if it is an insect? Photographed in Germany.
It's hard to tell from your photo, but you should check whether Macroglossum stellatarum (German: Taubenschwänzchen/ English: hummingbird hawk-moth) looks similar to what you've seen.
This moth is living in Germany (and other regions) and due to it's way of flying (hovering and audible humming) it's sometimes confused with a hummingbird.