Use ramp and steps meshes as actual ramp in unreal engine 4.26

It sounds like when you’ve imported the mesh, Unreal has auto created the collision and created it as a simple box collision.

To change it, you need to double click on the mesh itself, choose collision from the menu bar (the green odd shaped cylinder) and select whichever option is needed to highlight your mesh in a coloured box. This is your collision.

Go to Collision on the top menu, select remove collision then whichever option highlights your mesh in the best shape possible:
Unreal UE4 Collision options list