I have not done any research in Germany or Switzerland. You need to find the town they were from. Records were kept at the local level.

This is a website you might try.
http://www.geneanet.org/

It is popular in Europe and has many user submitted family trees. It has all the same problems as user submitted trees at Ancestry but maybe it can give you an idea where the surnames you are interested in are most common. If you get lucky you may find a tree submitted by someone that speaks English. That happened for me in France.

I searched for both Geiselman and Geissman in Germany and got a few matches on both names.

Curt