All my previous BMWs have had the facility to set a speed warning which sounds a tone when you exceed the set limit.
The X2 also has this but as soon as the engine is off and the system shuts down the setting is wiped.
The lane warning is not working either.
Dealer has tried to fix including software update and they don't seem to have any idea what to do.
Usually, in this case, I would try a different dealer, or sometimes emailing Mercedes corporate.
The other options are independent shops that specialize in BMW's but you'll be paying out of your pocket for car under warranty!