Amazing story 👏
I felt the same way when I started a full time job as a Junior Web Dev. I've built websites before, always from scratch. The first few months on the job was very humbling. I realized how much I had to learn.
My boss and senior devs were very helpful. I started learning Backbone.js and D3.js which were part of the stack and around the 5th month, I got a huge task which was an important part of the app. It was an amazing learning experience.
Never stop learning. Good luck!