I purchased this theme for my website. I installed the elementor plug in but when it was time for me to use elementor the website would crash by displaying only code.
I saw your shared video and it seems you are trying to edit the page using elementor but the page is created using WPBakery page builder.
You can create a page using any page builder but can only edit it using the same page builder which is universal for all themes and not specific to the Jevelin theme.
Please advise if you have more questions.
You can request a refund from ThemeForest where you have purchased the theme.