XnView Software

How could I change (every of) the EXIF data? E.g. the GPS data?

you can't, for GPS you have 'Edit GPS'

Many thanks!

May be you could tell where I can find it, that would be tremendous.

Is it generally not possible to edit the others or most of them?

There are several ways of modifying exif data;
the method you choose depends on the number of photos you want to process, or the number of fields you want to modify.
- In browser mode, you can modify three exif dates: Tools > Modify timestamp
- You can also modify GPS data: Tools > Metadata > Modify GPS
- You can modify 5 other Exif fields using Tools > Metadata > Transfer ( Add > Exif > choose from the list) as target fields (and use other metadata , or text, or nothing as the source).
- You can clean all exif data: Tools> Metadata > Clean > ...
- You can use existing Exif data as a data source in a number of menus (labels, renaming, etc.).
- You can view exif data in the ExifTool tab of the "Info" panel.
- I often use an external addOn in Tools > Open with > Configure programs : here Exiftool can be called to do specfic processing ...
( viewtopic.php?p=183222#p183222 )

Let us know what you need, maybe we can find a solution ...

Thank you very much!

So it seems as if one could edit / change each or almost each value / information.

I just wanted to upload some images and remove / change some ("private") meta data not to be published. That is doable now, so I for now know everything I need to know. Thank you, yes, I will ask again if need be.

Many thanks again!