Galaxy S5 overheating is normal?

I play GTA SA in high quality and in a few minutes it is slow, Temple Run 2 loses many FPS, GodFire falls from 60FPS to 30FPS or less, Asphalt 8 begins to have low FPS.

I analyzed the performance of the GPU and CPU:
The phone heats up, reaches an average temperature of 70 ° C (158º F) ~ 80 ° C (176º F) , gives peaks up to 90 ° C (194º F) on hot days.

The GPU performance drops a lot.
The GPU performance falls gradually from 578 MHz to 190.73 MHz and no longer increases until the temperature cools.

I live in Brazil and in recent days made a lot of heat - 32 ° C (89,6º F), is now doing 15 ° C (59º F) and the GPU performance drops to 305 MHz in less than 10 minutes.
I have the S5 makes a week! I received from the Samsung because of problems with the S5 Mini GPS.

This is normal? Or my S5 has problems?:confused:

Thanks in advance! :)

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