Natalia,
Since you're looking for suggestions on beers, then it is good that BERLIN is on the list of destinations. I would definitely recommend that one mentioned in the posting above----BERLINER WEISSE mit rot. Mit grun is ok, I like the raspberry taste better, ie., mit rot. Two other Berlin beers are definitely worth trying, aside from BERLINER WEISSE mit rot, (one of my very favourite beers in Germany,)---BERLINER KINDL and SCHULTHEISS
In Paris I would recommend the 1664 Kronenburg, just ask for a "soixante quatre."
If you decide to go somewhere in the western part of Germany, go to DORTMUND for their beer, all of the various Dortmunder beers are great.
And, if you do go to ERFURT, try the beer RADELBERGER; prior to reunification it was considered the best East German beer; now that beer and its reputation are even more enhanced--definitely worth it.