Second side of my object renders weird?

Hello, Im trying to render a 3D OBJ model, mostly everything renders fine, but for example, here:
How it should look? Well, atleast there should be no completely black spots, anyways, the back/second/whatever side should be like a copy of the front. Can anyone tell me, where Im doing the mistake?
Thanks for any reply

Both model and texture are fine - after plugging it into Blender it seems that the UVs are not normalized though.

Either normalize the UVs to stay within [0; 1], or set the texture to repeat after loading it (example):

new THREE.TextureLoader().load(textureUrl, (texture) => {
  texture.wrapS = THREE.RepeatWrapping;
  texture.wrapT = THREE.RepeatWrapping; = texture;

Thank you!!!