Multi step form with responsive page with Vanilla Javascript

This project was very challenging, especially in making it responsive also the JS part was not comfortable to make as I am not that good at JS I just knew the fundamentals of javascript but I can say that I can create something bigger with basic components and that's why the JS code lines are almost a thousand though all of them are functional and works perfectly. but it was so a fun and interesting project I can say. Anyway, I would like to know something more that I should have used on this project if you have any suggestions I would be happy to learn new things from you.