License and CC0
Many images here are under CC0, since you cannot release your work to the public domain in Germany.
Follow the link above to learn about CC0 and how you can use CC0 work.
If an image is released under CC0 you will be able to find such a note below the image and/or in its meta data. If you do not find that note, the image is probably not under CC0. Especially images containing persons are not under CC0.
There are images where I am not the owner. You can find out who is the owner of an image by looking at its meta data or the information given below an image.
When using my CC0 work it would be nice to give me attribution if there is an appropriate way to do so. You don't have to, in which case I don't like you personally.
If you build upon my CC0 work it would be nice to release it under a free license.
Releasing my images under CC0 is more like a project. In the end I might or might not be disappointed about society and/or single persons. My profession has nothing to do with selling images and allows me to do this without any risk.
I believe that a strong public domain would boost society a lot. Every single person could build upon the work of millions. The internet gives us this chance and we better not screw this up.
If you want to use images in a way that is not allowed by its license, if you want to use images that don't have a particular license or if you need higher resolutions of images you can contact me.