Getting posts from another WordPress site

Hi!
I want to display posts on particular wp site from another wp site. Bascially, I would like to have kind of category of fetched posts or just modified avia shortcode plugin which displays custom blog posts. I thought to use WP REST API to get posts from the second wordpress site.

I have created custom avia_shortcodes based on “blog” and “postslider” plugins because I am using grid layout to display main posts. Then, I would modify source of displaying posts, but I couldn’t find the file or place where entries are fetched. There is just a foreach loop which iterates on
($this->entries->posts as $entry)
Where can I modify the source of posts which avia_shortcodes are using? Or maybe you can propose whole different approach?
The goal is that these two WP sites will display common posts among themselves. After click on particular “another” post it should redirect to the specific post on “another” wp site, so it is not needed to display full post content on that site.