I play on a laptop and get 60 frames most of the time, first off what you should try doing is opening up your documents and going to the folder Arma 3 - Other Profiles
and opening a notepad, it will be what ever name you play in game with <- It will look like the 2nd name in that picture and after you open the notepad scroll to the bottom where it says scene complexity and set it to 200000 no more, no less.
This should up you about 20-30 fps.