I don't understand, you said that you enter Janda as the keyword, you should be entering it as the Surname. You may not find your family here at ancestry as the German collection is still pretty limited. It may be necessary to use the libraries at your local LDS church. Since you said that you know the city you can look for church records on microfilm. However a city as large as Lubeck will have lots of churches.
I was able to find my German roots using these microfilms, it takes time and patience and the ability to read the old German handwriting.