All white and untexturable part of my mesh It my 2nd week of using blender and still learning. My problem is a part of my mesh is untexturable and all white but my mesh is not 2 or more objects its only 1 joined mesh

heres my blend file
It's because these parts of the mesh don't have the Material assigned to them for some reason. Select these parts in Edit mode, then select the Material in Material slots and click Assign.