The start of the 2018 season has been a frustrating one for Heimgartner. He returned to a fulltime drive after a year out this season and has shown some promising speed at times but hasn't been able to put together a complete performance to earn a good finish as yet.
"Obviously the results haven't come our way for various reasons but we have shown good speed at various points throughout the year so far," the 22-year-old said.
"It has been positive. You want to get those results but we are just building and learning.
"I think I have performed well within the team but there are a few areas I need to improve on – nothing I have been doing is perfect so I will have to keep chipping away at that."
Nissan has made some significant improvements this season but they have been hard to see as other teams have also picked up their performance.
"We were about four tenths faster at Tasmania last time out and we have made big gains with how the car performs on the track," Heimgartner explained.
"We are making gains but unfortunately no-one else is standing still.
"The new Holden has come in and it is obviously very quick so we need to adapt and catch-up to them.
"Red Bull and those teams week in and week out add those one percent things and they add up.
"The equipment we have got, the team we have got is all capable – we just need to put it altogether to get a result."