Well, the Flak 36 is the mighty Eighty-Eight Gun, the famos 8,8cm gun. That gun ja absolutely able to penetrante and sink a destroyer.
And even a 3,7cm or 2cm gun could be able to penetrate as an destroyer of the Fletcher-Class for example had a maximum armor of 19mm. But I don’t think they would be enough to sink it.
And yes, they were able to aim downwards for some degrees, as an airplane could fly deeper than the position the AA-Gun ist positioned (Hills) or, and far more important, to use them against targets on the ground.
