How to use 3D model on 2D Game with collider and Gravity? Please give me some Guideline.

i had spent a week on this, but i really cant find any tutorial or example to show how "3D model" can put on 2D game with Collider and Gravity. I had try to use rigidbody2d or rigidbody with Physical or Physical2D, to do, but the results is very weird.

when i use rigidbody and Mesh Collider, the "3D Model(Character with idle animation)" will fall to facing floor or keep rotate after touch another Collider Box. and when i attach the "Mesh Asset" to the Mesh Collider, the "Mesh" Collider like 90 degree facing on the floor, but i cant adjust it.

if i use rigidbody2d with Polygon Collider, the Collider area is not really same with the "3D model" when the animation is move. Example, when i "move left or right" for the "3D model", Collider part is not equal with the 3D model itself.

now i really confuse, is that got any tutorial or guideline to show me, which way i should use and how make the 3D model able work on 2D game. Or what i really miss on this part.

thanks alot!