@Redsandro: To workaround the cache problem, edit openstreetmap.dgml and increase the cache timeout. It's currently one week.
I guess that the root of the problem was an Internet connection where you get some login screen. When requesting a tile update, instead of the .png file the .html login site is then saved to the cache. Since it cannot be loaded as an image, you get pixelated images. I filed bug 279431 for this.
For the search problem, can you check whether there's a .sqlite file for Berlin somewhere in /home/user/MyDocs/.local/share/marble/maps/earth/placemarks/?

@marbleuser: You're right that Marble generates the turn instructions itself and omits instructions when the street name is the same. My intention to implement it like that was to avoid a huge load of unnecessary instructions for each and every curve. I can play with disabling the check to see how noisy the instructions get.

I'm out for three weeks now, expect no posts here in between. Please keep voting for
Marble 1.2.0-1
Marble Maps 1.2.0-1
monav-0.3
though