Ideapad 330s processor issue

Hello 

I have small problem and I will be happy for your help.

If I play the game after few minutes the processor frequency drops from 2,6Ghz-3,4ghz to 1,49Ghz and the game start lagging.  The cpu frequency is still 1,49 till the end of the game, sometimes after few second the processor is again alive, but sometimes is still 1,49Ghz does not change and I have to restart the notebook.

All temperature are okay around 75C. 

Is this normal? :/

Thank you for your help