I would like to change some textures by myself. But i dont know how to put the xnb files into my GIMP 2 program. I installed "GXView", but I dont think, that it helps because when I open a file its just black. Can anyone help me?
I don't think GiMP 2 can read. xnbs. If it could then I likely would have already been doing that. However, there are plenty of tutorials on how to unpack .xnbs with XNBNode, converting them into .PNGs so you may edit them with GiMP 2.
What about a program like Paint Tool SAI? Is it the same process? Also would you know how to put them back into the .xnb format to mod back into the game?
XNB Node can both pack and unpack .xnbs, here is a guide. Any questions, just ask, I or some one else will be happy to help. Happy modding!
I'm sorry that I didn't reply sooner, and I see the question is answered, but I feel I should still respond: I've never heard of Paint Tool SAI. Personally I use Paint (Windows 7-10), and Paint.NET to edit the PNG of the sheet, and then as mentioned above re-pack the .xnb If it can edit .PNG files then the tutorial above applies.