and the negative voltage displayed on the 20x4 lcd is displayed very fast.
and the positive voltage displayed on the 20x4 lcd is displayed normal

i doubt many would risk unvetted zipped content from google drive, youtube would be safer.
what does displayed very fast mean ?
what does displayed normal mean ?
has it ever worked or is it just a proteus simulation, proteus does not really work for some real time things.
there is no schematic.
why use fp ,can you really expect accuracy to 2 decimals.
what does symmetric power supply mean ,the code is just a display
two dp accuracy from single asynchronous adc results is not plausible afaics esp without a stable voltage reference for adc

[same old same old]