You can add more meta boxes – with simple text field editors or TinyMCE editors with more functions – in admin, and then call those meta boxes in your page template.
This is a very common thing to do in WordPress, both in a UX sense for the user to be able to add content, and because – as you have discovered as a site admin and theme developer – the function the_content() can only be used once in the loop and wasn’t designed to be used multiple times.
Best thing to do is take a look at some plugins that enable you to add and configure the display of more meta boxes. The most popular and extensible is https://www.advancedcustomfields.com/
And do a search for other similar questions: https://wordpress.stackexchange.com/search?q=advanced+custom+fields regarding that plugin.