[Ataros]

Every patch makes game files more and more fragmented which naturally leads to reduced performance.

Try using e.g. Gamebooster to defrag the game files before trying reinstall. Steam defrag does not work well enough for me.

You may also try backing up controls and info-windows settings files and then delete the 1C-Softclub directory from your documents folder completely. Then check game files integrity in Steam and run defrag.

Also make sure you reinstall all programs from Steam\steamapps\common\il-2 sturmovik cliffs of dover\redist folder and check Internet for their updates. Complete game reinstall probably reinstalls these programs.