Hi,

Try restarting your computer and then verifying the integrity of the game cache for Arma 3.

1. Restart your computer and launch Steam
2. From the Library section, right-click on the game and select Properties from the menu.
3. Select the Local files tab and click the Verify integrity of game cache... button.
4. Steam will verify the game's files - this process may take several minutes.

Try all of the possible solutions listed on the Arma 3 Unusual process exit article on the Bohemia Interactive Community Wiki.

Try switching to and playing on the profiling game branch. After downloading new data verify the integrity of the game cache.

• profiling branch (special performance + profiling build - requires access code: CautionSpecialProfilingAndTestingBranchArma3), alternative download of needed binary possible from Dwarden's dropbox

Try to delete your profile folder (create a backup) a try to start the game.

The file yourprofilename.vars.Arma3Profile must be deleted.
Path: C:\Users\*username*\Documents\Arma 3

So, there is some next solutions.

try to decrease your graphic quality (if you're using ultra set high or medium). It´s possible that your have no more space on your GPU.
reinstall your GPU drivers