I can not remove noise after 8000 samples

after rendering with 8000 samples and test dozens of configurations can not do a clean scene. My main problem I think is the indirect lighting, I have no problems with fireflies

1 sun + 1 hdri + lamps
bounces max: 12; min: 4; diffuse 4; glossy 4; transmission 12;
-I tested with AO and helps a bit but does not look very realistic
-I tested with 12000 samples and the problem continues

hi you can check your hdri if the resolution and the quality are enought . disable it and make a test render

Unfortunately to the render-time conscious, this is to be expected in a undirectional pathtracer.

Indoor scenes with small lights will tend to require a lot more samples than say, an outdoor scene or a scene with large lights (on average needing 20,000 samples or more). You will need to wait for implementations of things like adaptive sampling if you want to avoid the use of as many samples.

You can however try to create your own de-noising setup in the compositor to try to remove the remaining noise, but making a good setup can be tricky and most just use a 2D program with filters. Now a Blender compositor setup making use of bilateral blurring or other smoothing setups could actually work here because you only have like the remaining 5 percent of noise to get rid of.