An Appeal: " Dear Sister do you have any advice on how I can find my black father again"

I received this letter a few weeks back and after communicating with the sender, he gave me his concert to publish it. This is a call and any piece of advice or information will be greatly appreciated.

Hi "A Sister in Germany" I do not even know your real name but I guess that does not matter at the moment. You might be able to help me here comes a lengthy story. 
I was born in 1964 in a smaller town in Southern Germany, Reutlingen. Most people never had seen a black man back then. When I was two years old a really tall black, really black man moved into our house, his name was Aliou Diallo from Guinea living in Conakry. He wanted to become an electrician and his country had sponsored the education in Germany. My father who was an electric engineer looked after him and took him in after no one in the town would liked to have a black man from Africa near them. So Aliou looked after me for the next three years of his education after work and I became black. So what happened to Aliou after he had finished successfully becoming an electrician? He went back to Guinea to support his family and country but got imprisoned because he went to West-Germany instead of East-Germany. Guinea back then was supported by the Soviet Union and he had to be in jail for one year, afterwards he was deported to Senegal and this is where my family lost track of him. Dear my Sister do you have any advice on how I can find my black father again or at least his family? I am really appreciating your help and any advice on this matter. 
Aliou was not married back then and would now between 70 and 75 years old. I have his last postal address from 1970 when he wrote his last letter from Dakar.  
Here is the last address we had:
Aliou Diallo s/e de Tehekowra Samake Parcelle No 305, Grand Dakar, Republique du Senegal


Vielen tausend Dank, Uwe