Responsive HTML-CSS-JS - Crowdfunding product page solution

Hi, This project was really challenging, but I was able to complete it, took me a while.

Questions: I would like a review from a senior front-end dev about my solution.. and know, for example:

• How would they handle turning the total amounts from text to numbers and removing the commas and add them latter. is my approach decent??

• Is the way I divided my CSS in different parts ok?? is that the way to do it??

• How can my CSS and JS be improved overall?

Thanks.