I like guitar, but it's """"""""

Your music theory is not very good, and it is difficult to learn to play and sing by yourself! In fact, you should not feel inferior at all. Many people don't understand music theory. Why are you afraid to ask the teacher? There is an old saying in China called "Don't be ashamed to ask questions". There are many things you don't understand now, so ask more! Learning by yourself will take many detours, and you can avoid these detours by consulting others at the same time. Just like you said, I stopped playing when I changed the key, which was caused by bad music theory. You can only score bullets, not be flexible. It's like you can solve a problem, but you don't know why. If you change the numbers, you won't. It's terrible. You don't need much music theory to play guitar, but you can't be ignorant.

I suggest you talk to the teacher. You don't need to learn music theory for long. Talk to someone. It is estimated that you can solve this big problem several times now! What's so embarrassing? Just tell the teacher, "I am poor in music theory, I hope you can teach me from the beginning." I believe that after you understand the music theory, you will begin to understand what you are playing now. If you throw caution to the wind, say you know nothing, so what!

Come on! Wish you success!