Ammonia levels always go low as nitrites rise. Nitrites follow ammonia going down. Partial water changes won't work by themselves as a 10 % change will only lower the levels by 10% and this method is a slow fix. If you are in a jam with levels, you might try a remover like Amquel+ or a detoxifier like Prime, then do some small changes, like 10% a day for a while. Read the labels carefully on any chemicals that you add.