You will not be able to get rid of the fade lines. That is the effect of the UV exposure. Over time as the newly exposed area now gets the same exposure it will lesson the effect but its not in the top layer of clearcoat so the buffing and waxing will only help if the exposed area is oxidized. The pigments in the base coat and fiberglass fade and the only easy way to fix it is a larger decal over the same area otherwise you can repaint or wrap the unit.
Same thing happens to cars if you a buy a new car you can remove the decals in the first year with virtually no shadowing.
This is also a common problem if you get your vehicle wrapped for marketing and then remove the wrap after 2 years any spots not covered by the wrap will have faded and cause the uneven shadowing in the paint.