Nyhus family from Gjovik

I need help with finding my ancestors from Gjovk, Norway. I have some information, but need to fill in some missing names and dates. My great-grandfather was Hans Nyhus and my great-grandmother was Marte Johannesdatter. In Norway I think Hans was listed as Hans Nielson. His father was Niels Olson. They lived on the Nyhus farm. As far as I know, there were five children: Ole, Johanna, Hans, Oleanna and Helene. Hans's brother Ole (Nielson) Nyhus immigrated first to the United States and then Hans came in about 1880. Marte and the children came in 1884. They had six children born in Norway and eight children born in the United States. Two of the children died in Norway, how would I find records of their death and I wanted to find out the ship they sailed on and more of the records in Norway. I have tried some of the web sites for Norway, but I can't get anywhere and I get frusrated. Any help would be appreciated. Thanks. Sue