welcome to the forum:)
80-85 degree C is an ok temp, according to the specs it looks like that card can take temp’s up to 97 degrees C so I don’t think you need to worry unless it gets near its max. to reduce the temp you should first check your card for dirt/dust and make sure it has good air flow, another thing you could do is download one of the many app’s that let you control the fan speed to help you control the temp, you can also turn down the graphics in UE4’s scalability settings to reduce the workload on the card but then things wont look as good.
that’s all I can think of right now, hope that helps:)