Hello there @Siriusjack7!
From your screenshot, that looks like shadow acne, a typical artifact caused by how the mesh’s geo is interacting with the light. That mesh has either a low poly count, or a conflict with its normals. And disabling nanite/lumen won’t affect the resulting shadow maps.
So, the very first thing I would try, if this was imported from Blender or Maya, send it back, and add a few more edge loops down the length of the wall. That way, the light will have more geo to bounce from, and should reduce the chance of getting those jagged angles. After that, recalculate the object’s normals (in Blender, for example, it’s done via Mesh > Normals > Recalculate Outside):
Finally, re-import the object to UE, and check if the shadow artifacts remain. If that’s the case, then the next step is to check how the light is affecting shadows. Select your Directional Light, go to its Details panel, and search for “Bias”. From there, bump up the values for Bias and Slope, test up to 0.8. You can also test around with Distribution, but it’s usually not needed:
If the issue still remains, you can adjust the engine’s virtual shadow bias directly, using cmdlet r.Shadow.Virtual.NormalBias. Try it with a value of 0.5, then move your light around to check for changes.