Update messed up my site

I updated the Shapely theme and it messed up my site by overriding the styles set in my child theme. Why is this and will it happen every time there is an update??

Thanks
Emma

Hello there,

I hope you are doing well today.

I am sorry for the inconvenience caused here.

Were you able to create a WordPress backup before hand?
Also, did you add the CSS code to the CSS file directly or did you add it via Appearance > Custom CSS?

Best Regards,
Support