For someone like me who doesn't understand German language, is it possible to go on with the daily life interacting with the locals in English?
Some rules of thumb:
1) The younger, the more likely to be able to speak English.
2) Rural area less likely to speak English (well) compared to big cities and tourist areas.
3) In IT/tech world in Germany you should have far less problems than say farmers.
I'd say those count in general though :) if you go to Amsterdam people are much more likely to speak English than a local, small Dutch town foreigners generally haven't heard about. And, English is very practical in our globalised world. Make no mistake about German though; it is also a practical language in Europe.
You should have it easy to get by.