Did you miss this?

Some numbers. This facility stores 1400MWh, on 2,000 acres or (~8,000,000 sq meters) Much greater then your 40,000sq meter estimate. Plus you said about 33GWh for a day. Well you’d need ~24 of these facilities to cover just Berlin.

You estimated 40,000sq meters, but that is off by a factor 2000. This is for a facility that actually exists. Theoretically it could be improved, but those theories aren't being built right now. So based on a grid storage plant that actually exists, berlin would need 48,000 times more square meters dedicated to energy storage then you estimated and in any case, THEY DON'T EXIST and aren't being built.