Hi Hannan,
Use a wood specific cleaner and a red pad under your buffer, you can either use the red pads as the extraction method (which means quite a few red pads) or if you work on no more than 10 sq meters at a time you can use more liquid and extract with wet/dry vac or carpet cleaning machine. This will leave the floor dull but grippy, if they want a better appearance and if the lacquer is still intact (ie no bare wood) then you can use a wood specific acrylic seal to give it a lift. Use airmovers between the cleaning and sealing to get the floor dry as quick as possible, don't use the very wet method if there are big gaps between the boards
Terry