this is reading from connecting earth and negative
There is no NEGATIVE wire in an AC supply it is the NEUTRAL
If you have 240 volts relative to earth on the wire you call negative then you have a polarity reversal. Live and neutral exchanged. This means your MCBs will be in the neutral and not in the live feed. This is
EXTREMELY DANGEROUS TO LIFE
The lead from the meter to the RCD is far too small. This is a
FIRE RISK as that cable will burn before the service fuse opens.
You are out of your depth, you are putting yourself and anyone using electrical appliance in the flat at risk and you have a fire risk from over loaded cables.
You have exposed terminals on the RCD that is loose and appears to be laying on metal tools, very hazardous.
GET AN ELECTRICIAN BEFORE IT IS TOO LATE