How would you design this level? Performance question

Im recreating a subway station in Unreal. The walls are quite complex. I have created them in blender. But placing only few decreases the performance quite a lot. How would you solve this? Im learning now Mesh Instancing as that seems to be the solution. But is there any other way you would recommend? I want to make the game for mobile. Will mobiles be even able to render scene this complex? Included pictures of scene and RL. If it would not be possile. Id use only 2D textures. Or maybe there is a way to make material with little Bump in the middle?

Thank you for your ideas.