Finish existing app in flutter ios native

Im currently working on a flutter project where im reading data in ios native from the Apple HealthKit, im running into some issues whichh i need help with. Get back to me if you can help. Thank you The backend is almost done, just a few fixes needed. Its flutter but most backend is ios native. in my ios part of my app im reading data from the health kit and i have to wait until the function is done and then return the data back into flutter dart and then i wanna create a graph out of it (my main problem is awaitng reply from query and sending it back properly