(I figured out how to word this without being rude lol) Usually that's a sign to experiment, then, because either shading method you are using is not suitable in that area, or you're too heavy on the layering. Your layering, as far as I can tell, is fine, though it's definitely a source of the monkey look due to the "outstretched mouth" look it gives, but that isn't really fixable, just a side effect on having limited canvas.

I played around with it a little bit and I made a few examples of what you could do, while trying to keep "monkey"-likeness low. A thing to remember is that due to limited pixels, there's going to be some resemblance of a monkey. It's really, at this point, looking for a solution that isn't giving up but doesn't give into merging Donkey Kong with the character in mind.

This is a rather simple change of shading, adding a few highlights and adding a tiny bit of shadows on the side:



This reshades the entire face, putting some darkness under the eyes to seperate the eyes from the cheeks, and adding highlight to where cheeks would be. (Makes the 'grin' look like its its own thing, not like the face is merged.) I can't remember who it was that I inspired this shading from but they do this often. Also added a nose, and a chin (though imho it looks better without a chin. I just thought I'd include it in case you feel differently, a chin is often better done with layering over it rather than it on the layering, but because part of the mouth is under the layers that isn't really an option at the moment.)



Alternative, the layering is entirely unshaded (save for chin if thats kept), but to make the face look more detailed the highlights for the cheek is moved under the layer instead of over.



And this is moving the angle of the highlights entirely.



None of these are, by any means, the best. But, at least to me, these are better options than leaving it blank. And they can be good starts to figure out a good shading method.
There's a few members I can suggest that do shading and/or hat layering tricks that are really good for inspiration and learning techniques. I do not recommend directly ripping their shading styles, just taking inspiration and forming your own from techniques you can see them use. Their names being, Purrfectionist, Leostereo, Kefka, ToeKutter, and DragonsDungeon.

Other than that, this is pretty much all I can do to help other than give words of encouragement. Take it or don't, its up to you what you do. I hope that this helps though and that you have better luck in the future. :3