I suggest to get yourself a simcard in your home country. Choose an operator
with affordable European roaming rates. Test the phone and stuff at home.
This avoid the hassle of getting yourself connected in each of the countries
This saves you visiting phone shops and trying to explain what you want and
probably get stuff you don't need anyway.
In case your phone gets lost with the simcard, ask for an extra "empty" simcard.
Your old number can be transferred to the simcard, using the long number
printed on it. The old sim card get disconnected in this process.
Print the support line number and put it with the spare simcard.
Alternatively, buy a German prepaid simcard from O2 or T-mobile
the best roaming options. You need a passport and something official with
your home address on it. Print the address of the nearest comm. shop from
the website shop locater and get things done locally.
Here 2 examples of getting a prepaid simcard in Germany; (its for 3G internet, but the process is the same)
O2 prepaid simcard in Germany
T-mobile prepaid simcard in Germany
Cheers!