Hi Diego, you should be able to fillet the top edges ok, like this:





The bottom edges will be difficult to fillet because of how your geometry is configured with this side coming close to being smooth:



Fillets can only be calculated on sharp edges, on smooth edges no fillet can be created and on edges that are very close to being smooth it makes things quite difficult on the fillet generator because the fillet will shrink to an extremely small fragment in those spots.

So often if you want to fillet something you need to construct it will all distinct sharp edges throughout and not have some edges that are to be filleted come close to being smooth with the surfaces on either side of the edge rather than distinctly sharp.

I'll try to come up with some recommendations a bit later.

- Michael