Regarding Theme Updation – How to install updated version of theme in wordpress

One of my wordpress theme is update recently. Now i want to replace that theme to old one.

My old wordpress theme is working fine but theme developer updates some good functionality in his upadated theme. So i want to update my wordpress theme.

Please help me what’s the process to replace updates theme to old one without loosing data/content and setting.

Thank You,

Vijay Gaikwad