If you move to Germany and start speaking German right away you will learn and improve a lot.
When placed in a German speaking school you will not learn anything but German for a few months, but after that you will not have problems.
When placed in an English language school, you will get less of a shock but it will take much longer till your German is up to conversation level and getting accepted in daily life outside school will be much harder.
So only ask for it when there are going to be a lot of English speaking teens where you move, like when you get to live near an base of the English or American forces (for so much as those still exist.)
Daily life will not be that different although sports might be organized differently. Not sure how much school teams are common in Germany. And some sports will be rare in Germany but others are common.
No problems at all if you play football (soccer) but cricket and rugby will be much rarer.
You will not like it in Germany if you behave like you do on Y!A - asking the same question for the forth time.
You will not have problems to fit in; most people will make friends with you since it is an opportunity to better their English skills. You really don't have to worry, just see what happens once you have arrived in Germany.
BTW: Your parents have made a good suggestion to send you to an English speaking school for at least the first and second year of your stay in Germany.
Foreign languages are never easy to learn....it helps if you have talent and true desire. Germany is also very nice. Enjoy. (PS: look at Deutsche Welle on Facebook and also nlfacile.com: both very helpful ways to learn German).
Try and persuade your parents to put you in an English school in Germany. So your not thrown in the deep end with language and life!
