You will receive the accumulated interest payments in accordance to the final maturity date stated in the investment information sheet. This means that counting from the day you transferred the funds into the trust account (payment date), the outstanding amount bears interest at an annual rate of 7.0 percent. After three years, the interest is due on 30.6.2023 together with the invested money.
Yes, the income from interest payments received is subject to general tax liability, as is other investment income. You must declare the interest income in your tax return. Unfortunately, it is not possible to submit an exemption order in Germany. However, you have the option of submitting a non-assessment certificate.