I try to paint a part of the object. I try to select it. In texture paint mode it's all greyed out. Why, and how can I solve the problem?
In your picture it appears you're in "solid view" instead of material preview or rendered.
Normally you'd probably want to be in material preview to see how things look. (Rendered is nice but uses more resources.)
Up at the top right of your screen where you see the 4 circles next to a drop down you can select wire frame, SOLID - which you're in, material preview, or rendered.
Edit: You have to pick material preview in both windows.
Hey Max,
You don't have a Texture Node Selected, so the Texture in Solid Mode only shows grey (Edit Mode Selection Masking):
If you switch to Material Preview, like Wardred says, you see the result of the second Mix Node, but you still need to select the Texture you want to paint on.
So you need to switch to material preview and select the texture. I will get back to you.
I redone the course completely and it was just fine. I don't understand what I did wrong. I was in material preview and I selected the texture node. So I still don't understand.
Blender system is convoluted, it's never been optimal. There are addons in the blender market that make texture painting much more intuitive and fun. You may want to go the market a go and see if there's anything there that interests you. Also check this list out that Jonathan Lampel put together:
https://cgcookie.com/posts/the-ultimate-2022-guide-to-the-best-blender-add-ons
None, I hardly use any addons. Not for any particular reason, just that since I don't do 3D as a full time job I've never had the time to sit down and see which addon would speed up my work flow, since I don't do any workflow because I only do 3D as a hobby. That might be starting to change though. I do use Wayne's camera rig addon all the time.