So I 've recently installed blender on my pc so and I want to learn some 3d rendering then I decided to directly skip how to build in blender and grab some of my build for the rendering and I got some errors

I tried to open it with the 3D builder... Well some of them got opened but the program say the file is broken then I should fix it with their feature once done with that fix I export it in. obj file and retry again but nothing works... except for that build from the user sadboye

I will upload the result of his render later.... But please how do I fix this ?