Outside the United States, the airport, navaid and airspace data is primarily based on openAIP.net and open flightmaps. Any change there will find it's way into Avia Maps the following week with the next in-app AIP update (scheduled every 1st and 16th of a month). If you encounter any error, we would kindly like to ask you to join openAIP.net and help update the data there to keep it up to date for everyone.
For the United States the data is provided by the FAA. If you encounter any errors there, please contact them.
In any case, keep in mind that Avia Maps is not a certified electronic flight bag and that you should always double check the data with an official source before flying.