How can I build a website similar to Trivago on WordPress
Wordpress is a CMS . Which is mainly focused on blogging. But , other wordpress developers can build additional plugins to add additional functionalities to it .
Trivago is a comparision website and it compares all the available travel websites.
Which just a simple algorithm, but to do this legally , you should have permission of those particular website owners.
And if you know PHP, go to wordpress developers, and learn how to make plugins for wordpress . Then you can easily install that and use at your own website.