Blender to unity issues

sample


Your main issue looks like you have your normals inverted(Most Unity shaders render only one side of a face). You need to recalculate these in Blender so they face outward(There are many many Q and A’s relating to this, Google if you need more info). After that you might want to look at Edge Split Modifiers or Baking Normal Maps etc to get the look that you want when in Unity.

If you go into edit mode and select all using “A” then on the left hand side click “Recalculate” under normals. If this doesn’t fix it try manually selecting only the faces that are messed up. Then underneath where you clicked “Recalculate” hit “Flip Direction”.