Hi @Kai74, welcome to our community!
Do I understand correctly that you aren't able to send photos using the Messaging application?
To use the service called MMS, you will need to download these settings in your device and you can do that in Settings > More > Internet settings > tap "Accept" and wait for them to be downloaded and installed.
Once they are installed, restart your device and send a message to your own phone number with a picture attached so you can check if it works or not.
Let me know if that helps and if I misunderstood your question, please do elaborate a bit! 
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