Can't delete Bing as search engine in Safari
The search engine of Safari has changed to Bing and now I cannot change it back. When I try Safari > Preferences > Search, and select Google, it just changes to Bing automatically. I have also looked in the Applications folder and I don't find any suspicious programs. I have deleted all extensions from Safari, too. What else can I do?
MacBook Pro (Retina, 13-inch, Mid 2014), macOS High Sierra (10.13.6), null