Hello!
The render is indeed not finished but also, I think I would try to add a light facing the character, can be dim just to unbug the shadow, and if you turn on the ceilling lights, a bigger one behind them to create what we call a ''rim light'' Dim lighted scene are the hardest to achieve and not have noise since lighting help clean the shadows.
On y end I render in a new window to check up on the render and stop it when I think it's clean enough.
(I render also in 2k to downscale after so the noise is reduced) And I don't use rendering Quality. Just Iteration.
To speed up the time you can also change the update from 5 sec to 30 sec so it update less often, giving more use for rendering