German and Australian taxes (Frankfurt)

Hi there, is anyone familiar with how Germany and Australia work with regards to capital gains tax? For example, I live and work in Germany, but have Investments still in Australia. I have to file tax Returns in both countries declaring the income from each one to the other (nightmare!). I have sold some Australian Shares in Australia and the ATO says I have to pay capital gains tax in Australia on the Profit. My German accountant says I have to pay the capital gains tax in Germany. There is supposed to be a tax treaty preventing me paying tax twice. Does anyone have any experience with this please?