Hello everyone !!!!

I’m a young trombonist and I am in need of help!

I suffer from a smile embouchure and as a result my upper register sounds tight, weak, and I can’t get past the C above the second ledger line in tenor clef, I don’t have much endurance either and I feel stuck trying to improve with by using a mirror for example but I feel like I’m going no where with this. Any advice ?

For many players the embouchure is a combination of smile and pucker. My advice is: find a good teacher.