How to make Textures?

My friend and I are making a game, two man army, and I have been trying to learn how to make my own textures but failing. I have no experience in making textures. I have gimp but still confused on going about textures. We are going for a more artistic kind of approach kinda like firewatch or journey where its more artistic base. It seems the textures are simple but I know there has to be more to it.
Questions if have

  1. where do I get the textures, google images?
  2. once I have a texture what next, I know for materials you could do multiple textures for roughness, metallic etc so would I just make simple ones and then combine it into the material?

Any advice on how to start would help tremendously.

You can get textures from a variety of free sources (To list one, or you can create your own by a program. Gimp is more for editing rather than pure creation, so find another program. Anyway, once you have the .jpg/.png whatever file, just drag it into the Content Browser and it is ready to make a material.

You’ll want to look up some YouTube tutorials about materials, I can’t explain the entire thing here.

Thank you should of know there was a website for textures. Also do you know or anyone know how to set it where the normal map resolution is around 1024x1024 or 2048x2048 while the distance background is of lower quality? To use less resources and when you are close looks good.

No, I haven’t dabbled into that yet, as I said, tutorials on YouTube should answer all the questions you have.