Hi @naturiste, welcome to our community!
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
You can either check with your operator if you can type in something before the number that you want to make a call to (I remember there at least used to be such a code here in the Nordics) or you can manually change the Caller ID in your device if you open up the Phone application > tap the three dots in the top right corner > Settings > Calls > Additional Settings > Caller ID > set this to "Hide".
I hope that answers your question! 
0online
1868962posts