Who can explain my new braces to me?

So I went to the orthodontis Monday and he gave me a removable brace to wear on my top teeth all of the time except when brushing my teeth until the end of January next year and thats when I think he will be giving me fixed braces on my upper and lower teeth. Could someone please explain to me what this removable brace actually does? Why doesn’t he just give me fixed braces right away, does the removable brace do anything to straighten my teeth? Also is it normal to find it REALLY hard to eat? How long will it take before I can talk properly because right now it sounds like I have like a really bad lisp. And I’m really worried about the hygiene of the removable brace. I clean it everytime I brush my teeth which is twice a day and after all meals and snacks I eat at home. Will it be okay? Like it won’t get germs or bacteria on it which will then go to my teeth/mouth will it? I rinse it with hot water and then brush on some toothpaste and rub it into the plastic bit and around the wires and then wash that off with hot water again. I also rinse the box you keep the brace in with hot water. Sorry for all the questions lol. Thanks if you do answer :) Oh and some of my top teeth are hurting from the brace will they be all right? I called the orthodontis today and the lady at reception said it would just be because I got it fitted only yesterday so might get some discomfort. I was worried incase some of my teeth fell out, could that happen from the brace? My teeth are really healthy, I have no fillings or anything and as I said I brush my teeth twice daily and then after every meal and snack. x