Yes you can modify the breakpoints but it will require some knowledge of CSS, PHP and Bootstrap.
There are two files you can modify.
1. header.php
2. bootstrap.min.css (located in /css folder)
3. style.css
This post will help you in modifying the Bootstrap Navbar, https://coderwall.com/p/wpjw4w/change-the-bootstrap-navbar-breakpoint
Let me know if you have any other questions.