In a bowl, combine the yeast and warmed milk. Mix well and let sit for a couple of minutes until the yeast is foamy. Add the melted butter and sugar. Mix well.
Add the flour and salt. Mix well. Turn onto a lightly floured board or counter top and knead well for approximately 4 to 5 minutes. Put the dough in a generously buttered bowl and cover with a clean towel. Let rise for 1 hour.
Punch down and place the dough in a buttered 9 by 12-inch bread pan. Cover and let rise for 30 minutes.
Preheat oven to 400 degrees F.
Place into oven and bake for approximately 45 to 55 minutes. Ovens vary so keep an eye on your bread. Tap on the bottom of your bread, if there's a hollow sound, it is completed. If not, bake a couple of minutes more. Remove from oven, let the bread cool in the pan for 15 to 20 minutes, then remove and cool on a wire rack.
Melt the butter in a skillet over medium heat. Add the cucumber, carrots, celery, olives, lemon juice, lemon pepper, dill weed, parsley, and salt to the skillet and mix well. Let those ingredients simmer while you dice the fish and shrimp into small pieces.
Add the fish and shrimp to the skillet, mix well, and cover with a lid.
Place bread on each of 4 plates. Check the fish mixture and add the cheese. Turn off the heat and cover with the lid. In a bowl, pour the lemon yogurt. Add the fish mixture to the lemon yogurt and mix well. Scoop the fish mixture onto the bread to your desired fullness. Serve immediately while the fish is hot.