Why is my quality in blender very different than unity

so when I made my model, I put it into unity and the quality was very bad. There were different colors, missing parts of the model. I really need help with this, I’ve been looking for a couple of days, but nothing is working for me, please help!

the black shotgun picture is in blender, the way I want it to look!
and the brown shotgun with a missing side and messed up trigger is what happens when I put my model into Unity.

  1. did you export the shotgun from blender? or did you just save the model in blender and import it into unity?
  2. the model is probably brown b/c of your lighting settings, is the color of the light that your using brown?
  3. did you rotate the model at all? that’s all the info that I can think of.