Create a child theme like the parent theme

Use a plugin.
I used Child Theme Configurator.

Okay, and what I have to set so its exactly like Nisarg?
Thanks.

Once you activate the plugin go to the configurator and choose create a new child theme, then click analyse. It will tell you if it can create the theme like you have it set up.
Then choose all the defaults and it will create your child theme. Activate the child theme after you view it to make sure it is all in place. Once in awhile you may be missing a custom header or some small thing, but easily redone. Without a child them you really can’t do as much customizing of the theme without it being overwritten when the theme updates.