it probably would help to see a floor plan as well as understand how things are constructed. also, what options do you have? can you tear open walls to add additional mass and RC? etc...
if its regular partition walls built on a wood stud frame wall, you could potentially remove one of the layers of drywall to expose the frame, add 100mm pink insulation, resilient channel. if its steel stud, you probably don't need RC but you'll still want to add the insulation.
then add 2 layers of 16mm drywall to each side, caulking and sealing. you need to do something similar to the ceilings - staggering the wall-celing drywall to get the maximum seal. remember to seal electrical outlets and switches.
HVAC will also play a role as it may need some additional bends and liner in the duct to reduce sound transfer between rooms. since you're effectively sealing the rooms, you want to make sure you have a return duct in each room as well as supply...
lighting should be replaced with track lights to reduce holes in the ceiling, or if you need to keep any recessed lighting, add additional drywall "boxes" around them to seal them off.
any doors between offices should be sealed so the entries are on hallway instead (if possible). shared doors should be solid core and doubled up - use good seals - like magnetic or exterior grade.
this should give you effectively an STC-50 or around 35-40db TL between rooms.
this should improve your isolation quite a bit using standard construction materials and in a building code friendly way. all of this is predicated on a structural engineer telling you the walls and ceilings will support the additional mass...