Best fit ram for ASUS ROG Laptop

[cyber_freak]

Hi,
I bought a ASUS ROG GL552JX-DM291D laptop from garg enterprises on ebay an year ago. It is facing some problems like Display driver stopped working and is heating up a lot. When I play games at low settings, Still it hangs up. It has an i7 processor and Nvidia 950 M with 4gb graphics but still the problem persists.
So I decided to upgrade its ram. Wanted to know how much memory can I add to this laptop and which would be the best ram for it?
Please suggest .
Regards.

 

[SaiyanGoku]

Heating issues can be resolved by cleaning up the vents and replacing the thermal paste. What are the temperatures while idle and gaming? Post screenshot of HW Monitor.

Lag could be removed by updating the drivers and ensuring that you aren't pushing the GPU to its limits.

Post screenshot of CPU-Z's memory tab.