There's no advice to give. Sorry.
You've no doubt seen my old posts explaining that cases wait in a queue until one of the Case Officers has finished enough of their current workload to be allocated some more. This will happen when it happens, depending on the volume of work going through the office at the time, and there's nothing anyone can do to hurry the process. All the timings given on INZ websites are never a promise, only their best guess based on averages of what has been happening, and obviously, there can be a sudden rush of applications which means the same timings don't apply by the time your case gets there. The cases now being worked on have to be finished before new cases from the queue can be taken on. INZ have done what they're supposed to do by giving you an interim visa so you are legal while waiting for the outcome of your application.