Bad lag/delay on arma 2 demo?

i have an 2011 HP envy 14 beats edition, 8gb ram, and an intel i7 quad core 840QM



i dont understand why the lag( or delay) when i play since my computer should support it.



its like everything i do on my computer(/ press the keys, use mouse) on the game it does that 2 seconds later any options on how to fix?Bad lag/delay on arma 2 demo?
The demo was always buggy as hell to be honest, The proper version, You'd have absoloutely no bother playing.