I trust you are reading the
nitrite and
nitrate correctly....these folks have given you good advice AT LEAST 50% changes every day until the NITRATE goes up and ammonia and nitrite are 0.....
The one thing I wanted to add is that even after your tank is fully cycled you have to do water changes, based on the test results, not on a "schedule", what I mean by this is that if the nitrate reading is over 20 you may have to do 25-50% change every other day to get them back down between 5 & 10.....it is not an exact science, but has to be adjusted to your particular tanks needs.