Geometry issues

Hello
I was given an asset to work with, but am having some trouble cleaning up some geometry issues I’m not sure how to clean up…I tried a few things but they seem to be related to a geometry behind the visible layer that is causing problems.
What would be a good strategy to make this cleaner?

Thanks!

File : https://www.dropbox.com/s/5by0mw9tuwwv4sd/TshirtGeo.c4d?dl=0

Screenshot with problems : https://www.dropbox.com/s/9c73gjg200rluyd/2021-03-02_17h11_27.png?dl=0