This code will help you to change base slug `courses` to your preferred slug, replace `example-course-slug` with your own slug.

tutor-lms-change-default-course-base-slug

add_filter('tutor_courses_base_slug', 'change_tutor_course_slug');
/**
 * @param $slug
 * @return string
 */
if ( ! function_exists('change_tutor_course_slug')){
    function change_tutor_course_slug($slug){
        $slug = 'example-course-slug';
        return $slug;
    }
}