Hey I’m new on this form. I got 2012 Audi a6 3.0t I was wondering if anyone know if I can do any tranny tune up beside fluid flush and filter replacement. I was thinking if I can do anything extra because it has some delays when shifting from park to drive and from drive to reverse but everything else is fine it shifts normally and when I need to speed up it also doesn’t have issues 

Oil and filter change is worthwhile, but if that does not resolve the fault it's likely the mechatronic control mechanism needs an overhaul. That's a job for an experienced mechanic.

So the mechatronic should be replaced completely or just replace parts in it? I was thinking about doing one more fluid flush and see if maybe this time will help more or it’s not worth it?

The mechatronic module is notoriously difficult to overhaul so is best left to a specialist. Try the oil and filter change as a first step.