Forgive me. I don't know how much you know.
CC3D does not have a baro or GPS and without these, what you are controlling is the raw thrust which translates into vertical acceleration/speed not vertical position. With very careful watching and adjustment, you can get it to almost stop at some altitude, but you must always adjust the throttle, even when hovering without drifting horizonatlly. The trick is to get it to stop at the altitude that you want. Then when you bank it, it needs a different amount of throttle from that. It takes a GPS and/or baro (or sonar) to hold a particular altitude. When driving a car and following closely, it takes constant vigilance and adjustment of the accelerator pedal to maintain a fixed distance to the car ahead of you. That is what you must do with the throttle to maintain a fixed altitude.
I have a ratchet on my throttle and when hovering, I am constantly adjusting one click up (it starts to drift up a little), one click down (it starts to drift down a little) to stay at one altitude.
Some people adjust the throttle curve (Vehicle tab) or in their transmitter to make the center part flatter. This makes the center less sensitive. Be careful. Your quad probably doesn't hover at exactly 50% and the flatish part needs to be centered on a horizontal line corresponding to your hover power.
There is a configuration issue where a powerful quad will climb at say only 15% stick when it should climb only when above say 35% stick. Is that your problem? If so, reduce PID D term as I mentioned earlier.
If not, a video with some verbal (English
) explainations of what it is doing, what you are doing to the sticks, and what you expect would help us understand what the problem is.