Fixing broken 3D models from photos typically uses software like Meshmixer, Blender, or ZBrush to repair holes, non-manifold edges, or mesh distortions.
First, identify the issue—holes (missing geometry), non-manifold edges (incorrect face connections), or warped surfaces. Use automated tools first (e.g., Meshmixer’s “Auto Repair” or Blender’s “Clean Up” menu) for simple fixes. For complex problems, manually fill holes or adjust distortions via sculpting or retopology (rebuilding the mesh for better structure).
If you’re new, try Blender’s free “Remesh” feature to simplify the model—this makes spotting and fixing broken parts easier without overwhelming you.