When full power is applied with the control wheel full back, the nose will initially rise higher than needed. At that point reduce the back pressure just enough to keep the nose wheel off the muddy surface. With the wings in this high angle of attack position, the aircraft will lift off into ground effect at an airspeed too slow to sustain flight above ground effect. Therefore, once liftoff occurs a slow but positive forward pressure must be applied to the control wheel in order for the aircraft to level out in ground effect and accelerate to Vx before trying to climb. The flaps can be retracted once the aircraft is climbing.
Ground effect occurs within one wing span of the runway, increasing closer to the runway.
It is the result of the runway surface interfering with the wingtip vortices and the average relative wind around the aircraft that produces induced drag. If the airstrip is soft, touchdown must be made softly on the main wheels and the control wheel held full back to protect the nose wheel. I once landed on a soft grass strip and held the nose off as long as possible as the aircraft rapidly slowed. When the nose wheel finally touched down at a slow speed it sank into the soft dirt half way up the tire. There was no damage, but the aircraft had to be pushed by hand to firmer ground.