Frontend Seniors/Middles, what I definitely need to know to become a frontend engineer?

Hello there, I want to become a frontend engineer, as you can guess))

I think that I have chosen the wrong path by starting with the framework (Vue.js) without basic knowledge of browsers organization, ES6 JavaScript, CSS and HTML semantics and best-practices. I think this list can be much more longer 😬.

Treat me as a junior engineer/intern in your own company in order to think of the best materials. Please, share your experience and attach some links to materials you find useful for a person who willing to be better in this field!