P.11 rules, be sures
Slow as hell but turns on a dime. 109 is faster, climbs better, dives better, has better weapons. In a 109 you'd fight it like you fight Zeros in a P38: DO NOT turn. You only turn when you pull lead, and extend when you can't keep the lead anymore. "Never turn more than 90 degrees with a Zero" was a P-38 pilot's guideline, and that also holds true with 109 vs. P.11. Keep the speed up, and there's no way he'll get his guns on you.
edit: Here's a couple of charts from Il2Compare. Treat them as a guideline, not the absolute truth.
Bf-109E4(blue) vs. P.11
Ju-87B(blue) vs. P11