how to turn off Private Browsing on Mac 10.13.4 safari

Open safari and its preferences , click on general > click on drop down arrows of safari opens with and switch from new private window to new window .Close the window and quit safari , for the next time when safari is opened it will open as normal browsing window , the indication of it is it has not a smart dark search field.See this article Browse in private in Safari on Mac - Apple Support

Safari File menu > Close Window (if you want to close the current window whether or not it is Private) then Safari File menu > New Window.