My felicia ran out of fuel recently due to a faulty gauge, if i fill the car up it will show full then make its way down to middle and doesnt come back down. Could this be related to a fuel sender problem or electrical problem ?

i tested the fuel sender unit. blue wire shows 8volts, brown wire shows 3.5volts and yellow wire about 8volts. how fo i test the resistance of the sender ?

Today tested the sender again and the resistance is 430 when empty and 420 when full. Also the resistor is rusted and the float is a bit punctured. Also a very odd situation is that when i lower the float arm the fuel gauge goes up and vice versa when im pretty certain it should be vice versa. Also the fuel gauge is not stuck it goes in all its ranges