If you are getting notifications from FlexibleSearch, then your Mac is infected with adware. FlexibleSearch is adware for Mac.
FlexibleSearch changes setting in your Mac. First, FlexibleSearch installs a browser extension in your browser. Then, after FlexibleSearch 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.