@sdpate, to prevent customizations from being overwritten with updates, if you have only CSS customizations, I would recommend using the Jetpack plugin which has an Edit CSS feature under Appearance which will keep your customizations safely saved in a different location so that they are not overwritten with theme updates. I see you have Jetpack installed on that site, but when I tested the connection, it comes up with some parse errors. You may have to disconnect it and then reconnect it.
If you have also modified theme PHP script files, or you do not want to use the Edit CSS feature in Jetpack, then you would want to create a Child Theme. You would then do all your modifications to the child theme so they are not overwritten by theme updates.