Don't file the sight! First, 75 yards is awfully far for what this pistol is designed for, it's not a target gun.
Next, what sight picture are you using? The Bersa sights are setup for a "dead on" hold at defensive ranges, if you are using a 6 o'clock hold it will be low. At 25 yds it will be even lower but not all of that is bullet drop, it is simply pointed lower, the more you increase the distance the wider the gap from your target.
Before you do anything, shoot it off of a sandbag or rest from 10 yards or so with a dead on sight picture, I'll bet you rip the center out of the bullseye.
You trying to screen for communists? Don't worry, we're all cool. - Dale