Hi @ChritsAlex, welcome to our forum!
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier to assist you.
I'm not quite sure that I understand exactly what you can't do. Are you trying to buy more mobile data from your operator, or is mobile data not working? If mobile data is not working, try downloading the Internet settings again. You can do so that in Settings > More > Internet settings > Accept > wait for them to be downloaded and installed and then restart your device.
Let me know if that helps and I'm sorry if I misunderstood your question.
