Unable to change search engine

I am currently running macOS Mojave Version 10.14.5 on my MacBook Pro

Every time I open a new tab in Safari this website pops up.(www.searchmine.net) This happened after I downloaded the adobe flash player. So when I tried to fix it by going to safari preferences > General > Homepage it wont let me change the homepage. It seemed to be greyed out. I tried to follow the advice on support page by quitting safari and then going to swww.searchmine.net) and opening profile. Under the admin prefs

On the search page. com , I am unable to click between the " " sign to remove the profiles as previously recommended

Also I find that there are two admin preferences now, which wasn't there before

Its driving me crazy!!! Please I need help!!!