Session lost

go to

Programme files,

steam,

steamapps,

common,

Arma 2 operation Arrowhead,

Expansions,

Battleye.

Run the BEService_x64.exe and uninstall battleye

Then delete the remaining files in teh Battleye folder.

-----------------Stage 2-----------------------

right click operation arrowhead game in steam.

go to properties

local files tab, then select - Verify integrity of game cache...

if it says to uninstall Czech addon, you can its fine.