Pharmon,
I'll add a couple of things that may be of help. Granny Smith is not self-pollinating. Although Granny is a late ripening apple it blossoms mid-season. Empire, Jonathon, Braeburn, Honeycrisp, William's Pride, Wolf River are just a few of the varieties that should make good pollinators.
Granny Smith does fine here in northern Michigan (Charlevoix, above latitude 45 degrees), with more color and flavor than it gets further south.
Apples require patience, 4 years is about right. Granny Smith and Honeycrisp or Braeburn would make a nice combination for the home garden. All three keep extremely well in storage through the winter. We were eating Braeburns up til about 3 weeks ago. Talking about these apples makes my mouth water. I can't wait for the season ;-)
Mike