Americans almost always pronounce "opportunity" as op-por-toon-i-ty. The "toon" sounds like "moon," not like chew. It's not like the British pronunciation. It's the same with words like "tuna," "tune," "Tuesday," etc. The pronunciation is like too-na, toon, Toos-day.
You hear things like "whatchu," "witchu," and others in hip-hop and pop music from the United States but in fact in regular conversation (unless you're in a lower class setting) you're much better off saying "with you." "Whatchu" is a very urban slangy way of saying "what do you." For most American speakers you'll hear "wa-da-yoo." So, "What do you want?" would come out as "Wuh-duh-you want" or "wa-uh-you want?"
edit: For "last year" Americans will usually say something like "lass year."
I hope that makes sense.
