To display all team members in ‘Expert Teachers’ section
Go to Appearance -> Theme Options -> Sections -> Section 4
and use below short code (just need to increase no.)
To display all team members as a slider, it will need to change some code.
If you want to do so, please send your website URL and WordPress admin login details for temporary at email@example.com so we can check and make change to implement slider in team members section.