Too hard

It seems lv 20 is the stumper. There are simply too many tanks to kill, and the il 2 dont make it better
No matter how many times I try, Ive spent the last month constantly getting swarmed in this level. At least give me tips on how to beat because Ive given up on this.

Panzerace1944 about ARMS ROAD 2 Bagration, v1.0.3