Eflite su 30 twin 70mm "Fly"from gras

I bought an Eflite su-30 twin 70mm, and fly from grass. I couldn't get it to take off after 10 attempts. Our airfield is smooth and is with short grass. 80 meters long.
I tried everything, move cg, extend the front wheel, flapron, in little wind, and in much wind.

Is there anyone other than me, who has trouble taking off from grass? With the beautiful plane!
If so, what have you done to be successful?