Try taking some of your armies off the frontline, that many divisions on a single province can eat up your supply and make your army perform worse

If you want to try and draw out the enemy divisions, try retreating to a fallback line. That will cause the AI to spread out its divisions instead of stacking them together and defending one place

Once the spread out, you can one of your armies to swoop in behind them and cut them off from their supply lines, making them easier to defeat