Mercedes E320 Fuel Gauge Problem

[nyko46]

This is what is going on with my 2008 E320 Bluetec fuel gauge:
On 12/06/19 I filled up my tank in a station where I always use.
As always the fuel gauge went to the top of fuel indicator.
My car normally drive around 620 miles with one full tank.
Driving the car normally, with less than 200 miles the gauge dropped right bellow 1/2 tank mark. I continued driving going and coming from work noticing the gauge going down faster than normally.
At around 300 miles the gauge went to "reserve light on" and after couple more miles the :message "Low Fuel" came on in the multi function display.
I then stop at the station to fill the tank again expecting an almost empty tank.
For my surprise the tank took only 10.18 gallons of fuel. Now I was expecting the gauge to go to the full tank mark but it went only to the 1/2 tank mark.
In the same day, driving the car back home the fuel gauge level went completely blank, showing no status of the fuel level.
Any idea about this symptom and why the "light indicator for low fuel level" and the "message on multi function display" came on if there was more than half tank remaining when I refill the tank?
Are there someone that had the similar problem?
What should I check first to troubleshoot this problem?
Thanks