Try using arma 3 launcher or a different launcher instead of arma 3 sync with only the mods necessary and in your startup parameters try: -cpucount=4 -world=empty -nosplash -malloc=system
NOTE: CPU count should only be 4 if you have a quad-core, if you don't know just delete it from the startup line
what does those parameters do? also i think i have quad 4.
The parameters do more or less what they sound like, for the most part.
-cpucount=4 Is for if you have a quad-core processor. It tells the game to use all four cores when the program (Arma 3) is running. Not all programs/games are coded to actually use quad/hex/8-core processors, so the parameter tells the program that you have a quad core, and so it should use them, even if it isn't natively known.
-world=empty doesn't load up the game maps on program start. Helps with faster game load speeds, and can help make the client more stable in loading (or so it's been for me).
-nosplash loads the client without splash screens (all those advertisements for game engine, nVidia "The way it's meant to be played", etc). Makes for some faster loading, especially in games where those splash screens can't be skipped (though in some games, this can lead to instability in client).
As for -malloc, I'm not 100% sure. It's not one I've often seen. Hope that's helped answer your question.