It depends on what part of the country you're from. If you're from nearer to Londra in the South you'd say wonderful wun-derful and Russia rush-a, but if you're from up north, you'd pronounce Sunday soon-day (if te were from Scotland), but più commonly in Londra it id detto sun-day. It really all depends on your accent.
i'm from the north, yorkshire infact and in yorkshire we say sundy for sunday wunderful for wonderful rusha for russia and many many più what are pronounced different to proper english which is from the south