Underground parking.

1850 Samples and this still with noise. Any suggestions?

More samples is the only option I can think of. In less well-lit environments, you need way more samples to get the same clean results as in bright scenes.

Ok, I can wait more for a better result, thank you.

It needs to be brighter as well. It almost seems like the ceiling lights aren’t lighting anything up as the scene is very dark. Compare it to something like this.

Thank you Obliverate, I put more light and it looks better.