Wordpress, how to deal with a large remote database?

Question

PHP

There is a small Wordpress site with an implemented tour booking system. Tours are posted there as entries.
There is a user's personal account, in which information about bookings and payment status is entered. All this is implemented by an already purchased template out of the box. And each round has to be hammered in by hand.
Recently, a JSON gateway was purchased to access a large database of tours. But I managed to process them only using Javascript (unfortunately, I'm not strong in PHP).
That is, I made a separate page with a search form, with each request there is an Ajax request to a remote database, it takes a lot of time to get the data (approximately 2 minutes). You can book a tour by also making a request through the gateway, and the booking data appears on the website of the service that provided this gateway.
But I could not figure out how to add this tour to the user's personal account on my site. Apparently this is done via PHP. But I didn’t manage to understand the template code to integrate this module into it. And in the search on the site, such tours are not displayed.
I wanted to know if there are any plugins or other ways through which it will be possible to automate work with a remote database through a gateway?
To use the received data to create tours through the implemented functionality of the template. Because, as I understand it, then it will be possible to reduce the time of interaction with the remote base, and include tours from the remote base in the site search.