Hi bartosh did you possibly post the wrong file? The one you posted is almost empty and doesn't have your shape in it.

re: sharp edges - most likely the problem is that you have "getting very close to not sharp" edges in these areas here:




that makes things difficult on the filleter to have surfaces come to almost be tangent to one another like you have there instead of more fully sharp to each other. The fillet becomes very very tiny or possibly disappears altogether in those smooth or nearly smooth spots.

When I was talking about making things sharp I mean a lot more sharp yet and without so much remaining bending in the surface shapes like you've got.

More something similar to this:

Start with an extrusion of a base form:




Use boolean difference to do a side cut to produce the sloped front:




Fillets:







- Michael