I gather there are two main issues, one on take off and one on landing - on take off you have very high rotor drag if you try to bring the nose up too soon and can end up with low speed and full power neither climbing nor accelerating and the answer is to lower the nose slightly which reduces drag and allows acceleration.
On landing the problem is yaw control since the rudder is usually behind the prop - good for take off with the propwash on the rudder but bad for landing when the power is off and the rudder can lose effectiveness at a higher speed.
As in all flying machines - poor technique will catch you out.