How to remove grey circles and add Fa Icons instead?

How to remove grey circles and add Fa Icons instead?

Hi,

how can i remove those grey circles on sub sub menu items that are displayed as a list. Normaly i think this should work within some custom css - but i can't find the right class as if i try to use  the inspector it changes dynamicaly.

Is it possible to use a icon from fontawesome (like fa fa-chevron-right) on those sub sub items?
I tried to enter it in the menu icon field but it does not work :(

The structure of the menu looks like this: (translated)

Poducts > Gearing Test > Noise and concenticity tests

Thanks an best
Ralf