A connection of less than 4 hours is only achieved when using the special ICE Sprinter connections. Compared to the standard connection, these trains skip some of the stops. The leave in both Munich and Berlin around 6:00, 12:00 and 18:00. The precise times can be found in the table on [this page][1].

Secondly, the search as you entered it in Google Maps suggests taking a regional train from Berlin Central Station to Berlin Südkreuz and only enter the ICE there. This doesn't make much sense as the ICE stops at the central station as well and pushes the travel time over 4 hours.
I suggest using the search at [bahn.com][2] instead. It's available in a couple of languages including English.


  [1]: https://www.zugreiseblog.de/zug-muenchen-berlin/
  [2]: https://www.bahn.com/en/view/index.shtml