Best thing you can do is use the Volksbund website (
http://www.volksbund.de/graebersuche/content_suche.asp).
For example, it will give you the grave of Johannes Gentzen (in Germany).
Search all your list, and then ask here only those that are not listed on the Volksbund for more details. You will have more luck to draw replies if you had already done a part of the work.
Best regards
Laurent