Hi @aj092,
nice that you contact our English community here again.
First of all, I would like to remind you, not to open different threads for the same topic. Therefore, @Sandroschubert closed the thread https://hilfe.o2online.de/o2-prepaid-19/ownership-transfer-for-my-prepaid-sim-548897 already for you.
In order to change the owner of your prepaid-card from your friend to your person, please fill out the following form: Change of Ownership
After you have sent us all the details concerning the new owner, you will be asked to do a post-identification.
I hope everything is clear to you now.
Loving greetings,
Tobias