Why My Laptop Games running slow?

This is My System

Lenovo Z51_70

Processor Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz

Video Card 1 AMD Radeon(TM) R9 M375
Dedicated Memory 4096 MB
Total Memory 4.0 GB

Video Card 2 Intel(R) HD Graphics 5500
Dedicated Memory 128.0 MB
Total Memory 4.0 GB

Memory 16 GB

OS Windows 10 64bit

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