Here's a list of free courses that I took in the past and currently taking that I think you should take to have a better grasp of web development. Most of these courses are introductory courses since they are free but nonetheless, having a good foundation can help you tremendously in your career so I highly recommend that you at least take one or two courses from this list.
This is a beginner introductory course about theory and practices of programming languages.
If you want to learn git this is the course for you.
At the end of this course, you'll have all the tools needed to build a responsive website.
This course is all about making your images responsive. I'd recommend that you take it after finishing Responsive Web Design Fundamentals.
Learn how to create images and interactive animation with HTML5 Canvas.
Your website should be accessible to everyone and in this course, they show you how you can do it.
Documentation is an important part of the development process and in this course, they teach you how you can write good READMEs.
If you want to get started with algorithms this course is for you.
Learn how you can build a PWA.
If you know of other free courses on Udacity share them in the comments!