Hi Gosd,
As HP says, make sure your on Hard flight settings, I find even stock CFS3 planes do wierd things when on easy settings.
on take off some planes will swerve to the left or right dependant on the rotation direction of the prop. try feeding power on gradually, use opposite rudder and if required a little bit of opposite brake pedal as well.
So build up speed with power gradually, if swinging left use some right rudder to correct it, if rudder alone is not enough to correct it, try a little right wheel brake, and if still having trouble back off the power slightly.
Also I dont know what install your flying in but ETO and to a lesser degree RS have cross winds build into some missions which will add more sideways movements to be counter acted.
hope this helps,
regards Rob.