If you are getting notifications from StartEssentials, then your Mac is infected with adware. StartEssentials is adware for Mac.
StartEssentials changes setting in your Mac. First, StartEssentials installs a browser extension in your browser. Then, after StartEssentials hijacks your browser, it modifies settings in the browser. For example, it changes the default home page, modifies search results, and displays unwanted pop-ups in your browser.