Have hot water dripping from overflow pipe & water is very hot(burning hot & have to cool down by opening cold water tap)

I believe recommended temp in the US is 120 degrees.

have to cool down by opening cold water tap) this is not only unnecessary, but it is costing you money. Harold is correct. Water heaters come from the factory set at 120°F. I turned my heater back to 110 and I don't have to temperate with cold water. The temperature is set too high. Reset the temperature back to 110/120. Good luck, Tom