Try holding the camera and GENTLY tapping around the rim of the filter and then try unscrewing it. There are small diameter camera filter "wrenches" available but HOLD THE CAMERA in your fingers etc. so that the torque is NOT BORNE by the gimbal.
I think I have seen mention of someone using a Phanton 3 propellor wrench with the propellor wrench lined with something to make it a better fit.
If it really proves stubborn I might consider wrapping the rim of the filter with a strong sticky tape and then with great care grip the filter with pliers but that would be a last resort.
If you are uncertain about a translation of that, check what is meant BEFORE you do anything.