Wordpress网站从同一台服务器上的另一个wordpress网站读取自定义帖子类型

I've seen some posts answers about using rss feed and rest api but i am not sure that will solve what I want exactly.

I have two sites on my server, both managed by me:

Site 1

| ---- Site 2

Site 1 is a magazine style site, posting news, reviews, columns, and general text. Site 2 is a members only learning center site (not a LMS site, just focused on learning). So it has Custom Post types for Learning Institutions, for their Principal and Teachers and for the offered courses.

What I want is to be able to create a post (normal or custom) with a Review or Article on Site 1 that let me choose which institution I am talking about, choose the teachers for those specific courses and have it posted with links that can show all the information from the institution and teachers on Site 1 (without sending the user to Site 2, because he wouldn't be able to access it).

I was thinking about creating the custom post types on Site 1 with the fields for choosing the institution and then the related teacher, a plugin for managing the post type and a widget to control how the information is presented on the frontend.

But I am not sure where to start and how to connect to the other database and stract the information. And I am not sure if that's the way to go with a plugin and a widget.

Thanks