@sven_md Trenchbroom is a map editor for Quake-engine-style games. I'm using it to create maps for some of my games. https://trenchbroom.github.io/
Its advantage is that it can only draw convex shapes, so it makes collision handling easier, compared to creating it directly with Blender or similar.
Thanks! Most of the wooden and metallic textures were made by my partner Biiscuit with Paint during a game jam :) And the lightmap helps for the "realism".