It happens that your mini helicopter can’t hover in one place in the air. Instead the helicopter moves slow or faster forward or backward. In most cases this is caused by an imbalance. The cockpit is too heavy or light and the center of gravity is not in place and the main rotors don’t blow directly downwards. Toy mini helicopters often show this out-of-box.
There are two fixes to solve this problem. The more difficult is to rearrange the placement of the accu in the cockpit. If the heli is drifting forward push the accu backward away from the cockpits nose. If the heli is flying backwards, you have to push the accu to the cockpits nose. Often this is difficult as the accu is fit tight inside the cockpit capsule.
It is often easier to add small weights. To stop the helicopter from drifting forward you have to place them at the rear bar. This will prevent the main rotor from blowing backwards. You can use the lever effect (move the weight) for fine adjusting this fix. I am using the fixing wires from the original packaging to do that. Correct backward drifting by putting more weight to the nose. Either from outside using tape or inside of the cockpit (if there’s room) or at the front ends of the landing gear using wire.