If your suspicions are true, it means that the person hacked your iCloud account or your Google account, and then connected to happn or connected to the app via your phone number and/or from your phone.

In the first 2 cases, it is necessary to contact Apple or Google directly and change your passwords. If you log in using your phone number, either someone has access to your phone or you have shared your credentials with a third party (which is against our T's and C's).

In any case, you can contact Customer Service as soon as possible, which will block your account while you secure your means of connection.