You should probably do some proper training in Maxwell first.
My Maxwell days are long gone, but this is like the first thing you learn, really.
A rendering in maxwell basically can't "finish". Instead it is cut-off at an arbitrary point. You can either set a time limit or you set the sample level it should reach. Back in the days of Maxwell 2 I remember it was set initially quite low (like 8 or so?), so just set that higher. I mostly stopped at around 15 I think.
Secondly use their denoiser.
Last but not least: Maxwell is a unbiased, physical correct renderer.
This means: Set your values correctly!
Garbage in, garbage out, as always 😉
What I have seen so many times is that people have totally white material in their scenes. You absolutely MUST think like the renderer, meaning you have to deal with physics. There no materials that are fully white nor fully black on earth. (They would be fully reflective / fully absorbent)
And so on, and so on.
Hope that helps with you endeavour.
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