Hello,
You’re going to need to have your theme author assist you.
The theme author has changed the styles.css, and for some reason- I am not sure why- has overridden the entire styles.css with PHP. There is a new page for styles, and it is all within php, not normal css.
For this reason I am not sure how to apply css changes to your site properly, as I have not dealt with this before.
Since this really is a theme issue anyway, not WC Vendor,s I am going to have to direct you to the theme author for assistance.
I have not seen that before. I am sure they have their reasons- but it is not something I can work with on my end.