Answer
You can deactivate push notifications in the settings of your XING iOS app. This means you will also stop notifications from appearing on the app icon that signalise e.g. that you have new messages or a contact has a birthday. You can also deactivate these via your iOS settings:
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1. Select Settings on the home screen of your iPhone or iPad.
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2. Scroll down to the XING app in the left column and select it.
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3. Press Notifications.
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4. Now deactivate the Badges option (wording may differ depending on your iOS version).