@Andreas ************
okay whether you had or didn't have a 60 day tourist visa and a 30 day extension has NO bearing on the amount of days you'd be stamped in for holding a german passport when you enter the country..When you stamp out of the country that extension (and the earlier entry ont he tourist visa CANCEL). You're getting a brand new entry stamp..
No matter if you crossed in by land or flew in you'd get a 30 day visa exempt entry. <- Now remember you can only enter on a 30 day visa exempt entry stamp by land two times in a calendar year (Jan 1 - Dec 31).