Hi I heard a teacher talking about secret trombone positions what are they do I have to get a special horn or mouthpisce for that I already have 17 mouthpisces which one is good for secret trombone positions do I have to unlock them or wat

I don't know any "secret" positions. There are, however, many alternate positions that can be used to make the slide movement better. For example, you can play F in the staff in 1st position or in 6th position. If your part has a number of switches from F to C, playing the whole thing in 6th can eliminate a lot of slide movement. I find two other useful alternates are Bb (top of bass staff) in sharp 5th position, and D above the staff in 4th position. In fact, D in 4th can be very useful since D in 1st is usually a little flat and there is no room to adjust it up much of the time.