Theme Horse

Hi b.shantiko,

Do you mean to say uninstall and reinstall new version? If then you may simply activate the WordPress default theme twentyfourteen/ twentyfifteen theme and delete the old version and download the latest version of interface and upload it and re activate it.
If you have made any customization on the core file then all your customization code will be lost. If no changes on the core file then you are safe to update a new version too.

Thank you!