Admin username and password

I have taken over hosting of a wordpress site, a friend helped to set it up for me, the problem is that the old host has the Admin username and password to be able to post blogs and change the site, i’ve asked for the password for the admin but he’s just not getting back to me, is there a way of overriding the old admin user or do i have to start again?

thanks

Jon Hunt

website is: https://www.doctorrevenge.com