Try the Modded Google Camera app from XDA link. I am using cstark27's app. It gives better results than the stock nokia camera app.
Hope they provide the pro camera app on the next update. Also don't know about the android one collab which hmd announced today at MWC. It will be good if our device is also included in it.
From the info i've gathered it seems like a Pro Mode app with full manual controls will be pushed to every ZEISS equipped Nokia smartphone, so great news. A bit late, but it's good that they are building on customer feedback and keep pushing things forward.
I just read that the PRO camera will come after Nokia 8 Sirocco is in sale (don't remember which site, maybe it was in an article on "Nokia Power User).
Just remember, it was in forum in this article: Nokia Pro Camera coming to ZEISS certified Nokia phones