DHL failed to deliver my phone ordered on contract and it was returned (but I received the eSIM letter).. what happens next?

Hello,

I had ordered online an iPhone 15 pro max 1T on contract, on the 6th of February and it was ordered together with the tariff O2 Mobile M Boost Online. DHL could not deliver the phone to my address, due to an error in the address in DHL database. The address in my O2 account is correct. However, the address in DHL database got truncated (probably during exchange with O2) → the building number is 1 instead of 1B. This is entirely not my fault as I have entered the correct address into O2 database while signing the online contract. 

Now the phone is on the way back to O2 and I have received an email from O2 stating that the order shall be cancelled once they receive the returned parcel. 

Meanwhile, I have received the letter containing the eSIM profile, which I have installed in my old phone, as I needed a German number ASAP.

Now what would be the next steps?

1. Can I continue with my sim plan? If yes, what will be the cost, will I still receive the Hardware benefit?
2. When I will receive my refund of the deposit paid (383EUR) for the hardware?
3. Will the handy contract be terminated automatically as the order gets cancelled? Will I be changed monthly for the phone as well.. or only for the eSIM? 
4. I do not speak German yet, I am new to Germany. How do I contact O2, if I do not receive refund and/or my bank account gets charged for monthly installments for the phone I never received due to a fault in the system (O2/DHL or both), which generated a wrong (with truncated house number) address?
5. How do I write to O2 privately in English, so that I can provide my order number and identification details, in order to get detailed status update on the whole cancallation process?
6. Is the hardware contract separate from the SIM contract?

Thanks in advance for your answers!

BR

Anshuman