Every time when i start Photoshop it says

[Johannes5E2E]

Every time when i start Photoshop it says that i need to change my workvolum because it is full.

So the problem now is that i dont know how and where to change it. 

Thanks for helping me .

[AxelMatt]

Here you'll find a lot of informations about that ->  Set up scratch disks in Photoshop (adobe.com)

[D Fosse]

Those instructions apparently assume that people make icons and thumbnails. For any real work, you need at least 100 GB, but if you want to be certain to avoid those messages; 5 to 10 times that. I would never work with anything less than 500 GB.