I'm not sure if we are searching the same family but I will tell you what I have.
My gggrandmother was Henriette Mielke, born in Germany, May 21, 1851.
She married a John (Johann ?) Pokrandt, then they immigrated to Inlet Quebec, Canada in 1884.
I don't know what Henriette's father's name was, but Henrietta named one of her children Bertha, and it was obviously a name used many times in that family. That same Bertha was my ggrandmother and my grandmother was Anna Bertha.
The fact that you too, have a Bertha in your 'group' leads me to wonder if we are indeed searching the same line.
If any of this sounds familiar, please contact me and we can set up a dialogue.