Exactly what do you mean by him being "really bad"? You said he is constantly squealing. Do you mean he's being excessively loud and screeching, or just making a lot of sounds?
Assuming that your issue is screaming, I can give you one method I've heard works really well. When birds scream, they are usually giving a contact call, meaning that they want to know where you are and what you're doing. In other words, they want you to respond with a sound, so when if your bird screams, and you yell at it to stop screaming, you're actually reinforcing the screaming by responding. The method I've heard is to simply ignore the bird when it screams and give absolutely no response. This means no sounds whatsoever--you talking, a sink facet being turned on, a floor creaking, etc. Eventually, the bird will learn that nothing happens when it screams, and it does not get the response it wants, and will, therefore, stop screaming. This method does often take some time, though, so you're going to have to be patient. Hope this helps!
