How to change admin user role to default? Can't access plugin settings.

One of my website was attacked by spammers and they injected some malicious files into the root files of wordpress.

I have removed lot of files manually but still my main problem is not solved.

All of my links at drbegani(dot)com are redirecting to some online pharmacy website and i can’t access plugin settings for most of the plugins.

I would like to know how i can edit the user role setting back to default for my admin account.

Any guide and help is appreciated, kindly treat this as urgent.