Hi @Rieks_k3
As this is a international community your previous post has been translated in to English using Google Translate. Please keep all future posts in English so that other users are more easily able to assist you. 
I'm sorry to hear this. 
I recommend that you try the tips listed bellow, check after trying each tip if the device powers on.
- Make sure you give the device enough time to start, press and hold the power key until the device vibrates, this may take up to 10 seconds.
- Make sure that the device is charged. If the battery is drained it may take up to 30 minutes before your device responds to charging.
- Temporarily remove any SIM or SD card from your device to make sure they are not causing this behavior.
- Force reset your device. You do this by pressing and holding the volume up- and on/off key simultaneously for 10 seconds.
- Perform a software repair using Xperia Companion.
Let me know how it goes!
