Google Chrome is not a search Engine, its a browser. You cannot use a browser as a search engine.
If you are using Safari as your browser the search engine choices are DuckDuckGo, Bing, Google ( the website, not Chrome the browser) and Yahoo.

Sounds like whatever Browser you are using, is now set to the weknow.ac website as its home, or start page when you open it.
In Safari, if you go to Preferences->General, you have the option of setting what new windows, and new tabs open to, as well as setting a start page. The Start Page is generally set to Apple.com, but the New Windows Open and New Tabs Option open is normally set to your Favorites, and not a specific search engine.
If you are actually using Google Chrome as your browser, you can click on the 3 vertical dots at the top right corner of the Google Chrome browser, and Click on Settings, then look for the section titled Search Engine. You can select what Search Engine Google Chrome uses as its search engine for the address bar there:
