GDevelop is a 2D game engine, so don't expect too much from the 3D side of GDevelop. The 3D in GDevelop is just an extension made by Pandako, which you can download here (WithThreeJS Extension for GDevelop by PANDAKO (itch.io)) and also Pandako provide example project but you need to pay $5 USD get the example project but the extension is free. You can watch this tutorial about 3D in GDevelop here.
3D in Gdevelop! - Tutorial - YouTube
First Person Shooter Camera in Gdevelop! - Tutorial - YouTube
Good luck!