[microtonal]

I am Dutch, but most of my PhD colleagues were from other (primarily European) countries. They typically didn't know Dutch. Some decided to do Dutch courses, others managed fine sticking with English.

Many European research groups use English as their main language for communication. Also, outside academia many people in Western European countries and Scandinavia are proficient enough in English to communicate with. (Though in my personal experience, English proficiency in Germany is quite bad compared to e.g. The Netherlands or Denmark.)