Update of 25 March destroyed previous settings I created

The Firefox update of 25 March has obliterated the previous settings I created. As a lady approaching 80, I am very disappointed, frustrated and annoyed that the settings I laboriously created have been obliterated by this latest update. So far, it is apparent that areas concerned are the appearance of the screen - location of bookmarks list, font size, task bar and menu bar displays, items included in the tool bar. My chosen browser is DuckDuck but Bing was reinstated. No doubt, further unwanted modifications to the way I wish Firefox to operate have been loaded. Can this situation be easily corrected or would deinstalling this latest update and reverting to the previous edition of Firefox return my chosen settings to me? May I say that I am not a computer "nerd" and am unfamiliar with much computer terminology and would, therefore, be grateful for any instructions to be phased in simple terms. GOW