Hello and welcome! Your first few days of the journey are going to be tough and you will need serious will power and lots of determination, but stick to it because it's worth it!
I think your first week's loss depends a lot on the total amount you need to lose - the more you need to lose the faster the pounds melt off in the first weeks. I lost over 13 lbs the first week, but then I'm quite a cow these days I think all but 2 of those pounds came off my cankles!
Good luck to you!