audi q7 2007 4.2 v8 Instrument panal lights is off and the car wontt working

I have an Audi Q7 2007, firstly I turned the key to the first click but in the
second click the car made a voice for 2 seconds but the engine won't work
i checked the battery it was too low then i tried again but the same thing
happened
When I tried for the third time i turned the key to the first click but no lights in
the dashboard turned on
then when I checked the battary again its level was 0
I charged the car battery using a cable and it charged but still, the same
problem when I turn the key on the first click no light in the dashbord on all
the lights off and I can't open the windows but the radio is on and i can open
the window using the key and I can control the car's main screen but the
screen on the  Instrument panel is off