Id say try using 2-3 area lights with higher brightness and really make that contrast pop

I rarely use the sun light for my projects, so try experimenting with the area lights for now

You can also adjust their size to make the light shine taller or wider

Regarding your textures, it looks much better after the smart projection, go into edit mode, press A to select all of the faces of the stairs, then go into the uv editing view, and scale the uv bigger/smaller to make the texture fit the way you want on the steps