Low performance / antutu score

Hi all :)
I'm using G5 H850 and:
when i play MKX Mobile for a while FPS getting low - i feel big lags
Antutu score is to low in my opinion.. When i'm watching benchmarks on YT or pics in google it should be around 130k (50k 3D score) any my is around 100k (30k 3D score)

I'm not happy with it - tought SD 820 would be much better than my friends SD652 (82k score) :/
Any ideas what could I do? :(

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