Poor service delivery from head office agents

Me and my wife brought vechile with platinum sticker gevin the all clear everything went smoothly for the sale of the vechile after first week there was drop of oil on my ground didn't take it serious cause the vechile was checked by dekra apparently and cleared.. yet engine cover show signs of oil spill .. on to the point I took the vechile for service to find the intercooler boost pipes is leaking oil and the is still only 3 months old by us nissan told me it's we buy cars problem cause within our 6monts period we as they must fix it.. my wife had to run up and down to places they send us waist Uber money.. we given a reference number being promised it will be sorted but mechanical shop is still waiting for purchase order to fix the vechile... the agents we email them no response after we send the quotations and millage.. it feel like they want drag it out until the 6month period is over then me and wife have to cover cost.. poor service delivery from head office