I would forget about the black, and do them all walnut.

I agree with @cat_ky ^ not black, it is too severe.

I am not sure I'd do walnut either, something lighter, the roof/overhang is going to darken the area. A light flooring material to help lighten up the space too.

No black beams but other than that I would need to see your house from further back to understand this huge heavy looking extension In the pics it look bigger than the house so more pics of the whole house please .I anot sure even about how this is built it seems not enough support for that huge roof but not sure

Few questions: what rooms face onto this patio? which direction does it face? climate in your area? approximate width & depth? what is going to be it’s intended purpose? TV? outdoor fireplace, kitchen , etc.?

I think there’s bigger issues than just the color scheme.

It's already pretty design incoherent. It needs unifying and simplifying.