ARMOSTHEUS:
Yes, Nokia Store has been now ramped down and replaced by Opera Store - this was announced already last year. See: http://www.microsoft.com/en-xm/mobile/support/faq/?action=singleTopic&topic=FA144235
Have you tried installing WhatsApp from their own site? I have not tried very recently, but these steps haved worked the last time I tried:
- On your phone, go to settings> security and check the box in front of Unknown Sources
- Download the latest version of WhatsApp on your Nokia X device from here:http://www.whatsapp.com/android/current/WhatsApp.apk. Wait for the download to finish (you can check the download progress in the Fastlane by swiping right from the homescreen)
- When the download finishes, tap on the downloaded WhatsApp.apk file to begin the installation
- When installed, just open WhatsApp and complete the verification.
Additionally - on Nokia X phones you can install other app stores to the phone, if you are not able to find all the needed apps from Opera Store. For example 1mobile, Yandex...