Problem with Importing a Mesh from Blender

Hi all. I have a problem with importing a mesh from Blender into UE. In Blender everything seems to be fine , but after importing the Toilet in UE it kinda looks like the inside of it like the bowl and the pipe are the most important part and the rest kinda get an invisible looking look, not matter which material i try. How can i fix that ? Any kind of help is welcome, would love to learn how to improve myself.