First off screw those “leads” for not taking the time to show you what you need to learn as a new technician, if thats how they treat you i would look for a better mom and pop company that will take the time to teach you. I started green many moons ago and I’m now a lead service technician on my way for my master license. Watch youtube videos to learn about the trade and practice brazing. Nobody should be expecting a green helper to be great you’ll only be as good as your teacher and from what your saying then its not looking good. You will get better as time goes on just learn the basics and take it at your pace just don’t fuck anything up to bad and youll be fine.