Dear @Adeeeioua,
Welcome back to the Wefugees Community and thank you for reaching out to us again.
First of all, I am sorry to hear about your rejection. I am not a lawyer, but I am afraid that it will be difficult to get issued a Duldung based on/because of your studies (whether you might have another reason to get issued a Duldung will be checked and depends on your individual situation). At the end it is at the discretion of the immigraiton office. We discussed a very similar question here.
The fact that you are holding a Greek residence permit probably doesn't help here. Exept that you might be able to apply (if meeting the respective requirements) for a corresponding visa for Germany for study purposes in Greece (apart from your country of origin). My colleague explained this here in one of your earlier opened threads as well.
Or do you assess the situation differently dear @mbeon-fardeen or @mbeon-Éanna?
In any case, I highly recommend you to get support in a counselling office - let us know if you need help with finding one in your area.
All the best,
Meike