How to calculate earnings in a TFSA?

Hi all, I am a non-resident (residing in Germany) but still have a TFSA in Canada since I plan to return eventually. Last year I had to withdraw $30k from the TFSA which was invested in mutual funds. I believe I have to pay 25% tax on my earnings (not the full $30k) to the German tax authorities, but my bank said that they don't issue NR4 slips for a TFSA, even for a non-resident. How can I possibly calculate how much of the $30k was earnings? I started investing in my TFSA over a decade ago. Or do I pay 25% on the full $30k? I have done a lot of Googling but haven't been able to find anything definitive. I appreciate your help!