Surnames

I am fairly new to the family history search and already have problems. I am looking for some guidance with the Digital Archives. I am looking for surname Hanson, but have been told that before my great grandparents changed it it may have been Johanson or variations of. 1st name is Nikolai, wife Minnie(maybe Mina or Wilhemina?) and they were from Drammen. I have been successful in getting the area and the Hansons but no luck in locating. Nik came over to Canada is 1903 and then had his family brought over in 1908 to settle. My grandfather was born in April,1895 in Drammen? along with his brothers & sister. Anyone have any ideas where to look next? Thanks for the help