Participating in a German company for retirement

Q 1: In 1977, I traveled from Syria to Germany to specialize in orthopedic surgery, and stayed there for six years. During this time, part of my salary was automatically deducted as a subscription to a German retirement institution that pays every subscribed physician the following: a. A lifetime retirement pension when the physician reaches 65 years old. B. A payment for each minor child. (Part No. 15; Page No. 312) C. A lifetime income in case of a chronic disability. D. A lifetime income to the widow and minor children in case of death. E. A lump sum of money for the widow soon after death. However, upon the end of my residence in Germany in 1983, I had two options: 1. To end my relationship with this institution completely, and recover 60% of the total amount that I paid during my time working in Germany. 2. To continue my monthly payments in return for the benefits that I would receive in the future, which I mentioned earlier. Some people advised me to choose the second option, on the grounds that returning to Syria is not possible for me, for some personal reasons. Consequently, my family’s situation will become difficult if I, for example, die or become unable to work for any reason, as they would not then have any retirement income. I was convinced by what they said on that day, so I have continued to pay the monthly payments. The surplus money that the institution collects is (Part No. 15; Page No. 313) invested according to the capitalist economic system. In a report issued in 1988, the institution explained that the investments for that year were as follows: 11% in building and housing, 9% in loans from which Riba (usury/interest) was earned, and the rest from stocks and bonds. However, if I change my mind now, the institution will give me only 60% of the total amount that I have paid up to now. I am, at the moment, reconsidering all my transactions to rescind all that is Haram (prohibited) in our religion. I therefore, need a Fatwa (legal opinion issued by a qualified Muslim scholar) from you as to whether or not it is permissible to continue my payments to this institution. I hope you will give me a detailed Fatwa on this issue. May Allah reward you!