I m sure you already searched at AlleFriezen.nl [https://www.allefriezen.nl/zoeken/persons?ss=%7B%22q%22:%22Salomon%20Levy%22%7D]. We, of the Dutch_Roots Project can help you lots at the Netherlands. But for good help at Germany you will need someone from there.
I am not sure if the German group is active. I tried to look into your family tree but as you re unlisted I can not see any info on your ancestors and what info you still need or what info you already have.
There are really many very friendly and helpful people at WikiTree that love to help at any.
I just can tell you from my experience @ WikiTree, WikiTree is really safe :) But we do understand you like to stay anonymous.
Staying unlisted will not be very helpful for you at finding family here or to find others researching the same as you do. Unlisted is really meant for children under 13 years. Please... and feel free to do or not...... as I said we respect your choices.... read here [https://www.wikitree.com/wiki/Help:Privacy] about the great privacy settings/possibilities at WikiTree for every profile you can set it different. And if you do not like your name shown all over the Tree, just use or an initial or "anonymous" for OR your first name OR your last name. Not for both....... If you need more info please contact a mentor at WikiTree.
Als je Nederlands bent en je wil meer informatie dan kun je mij ook contacten als je wilt of een WikiTree mentor.
Ben je Nederlands? We hebben @ WikiTree de meeste helppagina's in het Nederlands vertaald. Hier meer over privacy: [https://www.wikitree.com/wiki/Project:Nederlands_Portaal/Algemene_Informatie#Privacy_WikiTree]
I tried some at the German GedBas but it didn t bring much. [https://gedbas.genealogy.net/search/simple]
I am sorry I couldn't be of more help.
Kind regards from the Netherlands,