Make a hash of something - Idioms by The Free Dictionary
make a hash of something
make a hash of something INFORMAL
If you make a hash of a job or task, you do it very badly. The Government made a total hash of things and wasted a small fortune. She fumbled with the trolley and made a hash of stacking the food trays.
make a ˈmess/ˈhash of something/of doing something (informal) do something very badly: We tried making some wine, but we made a mess of it (= it did not taste good). ♢ I made a complete hash of the whole exam.