All the Android apps from https://play.google.com/store/apps/dev?id=6596947391073936664 are developed and maintained by Romain Pellerin, referred to as the developer.
The above-mentioned apps are, namely:
The developer currently resides in San Francisco, California, USA.
He can be contacted over email. You can find his email address at the bottom of this webpage: http://romainpellerin.eu.
Among the aforementioned apps, only Learn A Foreign Language collects user data, that is to say:
Deletion of this elements is possible by a mere request over email.