As the other comment said, the creaking is because of the floor boards and subfloor. It can only be fixed by rescrewing above.

The cheapest fix would be adding a second layer of drywall fixed to the existing w/ acoustical green goo (just google it for the brand). Use a diff thickness of drywall (ie if your current ceiling is half inch, use 5/8" for the second layer). Remember if you will also need an electrician to adjust ceiling boxes.

Better: remove drywall, add Rockwool batt insulation (gives slightly better value than spray and cheaper). Use z channel/resilient channel instead of strapping then do the double layer drywall as above.

It will deaden the sounds but there will still be creaking. Prob cheaper to buy your upstairs neighbour new flooring and subfloor