After buying the theme can i edit in elementor?

I wish to buy anahata theme, but I would like to use elementor as my editor can I use elementor or I should edit only with WP Bakery ?

Can I make header sticky in the same theme?

You can ask any pre-purchase questions via item’s comments page:

Yes, You can use elementor.

To be clear - this theme was not built using Elementor

Assuming the majority of existing templates/elements/shortcodes were built using WP Bakery, then these will not be easily edited with Elementor.

It may be possible to use Elementor to construct new pages and content, but given that the author does not list Elementor as being supported, I would strongly suggest using the link from @LSVRthemes to check