All you have to do is go to the “App Settings” page and tap on “Deactivate My Account”.
If you deactivate your account, you’ll completely disappear from the application. The people you crushed with won’t see you anymore, won’t be able to talk with you and you won’t be shown in the Timeline.
If you’d like, you can pause happn for 8 hours. Your position will not be updated, no one will cross paths with you and you won’t cross paths with new people. However, you will still be able to interact with the people you’ve crossed paths with, communicate with your Crushes and vice versa.