Do I have to migrate the contacts one by one or is there a way to export to a file from google and import from the file in DecSync?
As far as I can see, google allows exporting as csv, and DecSync allows importing vcf/ics files, so I would have to convert the csv to one of those formats if that is possible.
Yeah there is a way to export the contacts as .csv file. Try this out: https://support.google.com/contacts/answer/7199294?hl=en&co=GENIE.Platform%3DAndroid