Hi thani11
I am not sure your database will be lost or not. However, yo should backup all your site before theme has update. Here're some steps:
To update the KuteShop theme:
Step 1: Backup your site( Include codes + Database)
Step 2: From the dashboard>>Appearance>>Theme, you need to activate the default template( Ex; Twenty Seventeen theme)
( you can refer this document, it's the same http://test.kutethemes.net/koolshop_doc/#mazanoupdate)
Step 3: Click on Kutetheme and then click Delete( look down in the right). NOTE: DO NOT delete the Kutetheme-Child
Step 4: Return the dashboard choose Plugins then deactive the Kutetheme Toolkit, Slider Revolution, WPBakery Visual Composer and delete them.
Step 5: Return the Appearance menus choose Theme>>Add New>>choose your latest theme version>>Install
Step 6: Return the Plugins menus>>New>>and choose the Kutetheme Toolkit (Slider Revolution, WPBakery Visual Composer plugins are the same)>>Install>>and activate them.
Please do it and let me know.