Will this cause troubles like electric shock for me and fish and or heater failure?Rapid changes in temperature can cause condensation in for example cameras as well. Like Dee said let it come up to room temperature first
I could take it out for the night and let it adjust?Not sure as it is already in the tank. Did you get instructions with the heater or on the box?
A quick online search shows the heater is fully submersible and needs to be completely under water unless I am looking at the wrong heater.