Note 4 and Real Racing 3, low frame rate and some lags

I have a 910F (so snapdragon) Original Rom lollipop 5.0.1
I installed Real Racing 3, I expected a good quality and no lags... but unluckily there are a very annoying low frame rate.
What could be the problem?

If the problem is that default resolution is too high... there is some way to put a lower quality?