m15 R3, black screen, white boxes

Hi @Rackna welcome to this user to user discussion forum. This is not Dell Support. 

Please click on Product Support so that Dell can identify Model and Revision number of your laptop. Do not share your private system Service Tag or Express Service Code in this public forum. 

Is your operating system Windows 10 x64? 

Are these power hungry games, that require Hybrid Power from both ac adapter and battery, and does the CPU and/or GPU get very hot? 

Thank you for providing a good image of the laptop screen with random large 'white' pixilation squares on black screen. Sometimes this fault also has flashing squares. There are many coloured lines at the top of the screen, and your 'white' squares also contain many coloured dots. Sometimes moving the lid will cause/stop this fault, or Power off, then power on will give a normal screen. 

There are many fault conditions that will make the screen display this pixilation. There may be an issue with your graphics driver, monitor (hardware), corrupted system files, etc. 

Please: (1) Run the LCD Built-in Self-Test. (2) Check GPU, by connecting HDMI output to external monitor or TV. (3) Check drivers, by visiting Device Manager, do any of the drivers have a yellow triangle fault indicator, or group expanded with driver moved to the right. 

Please click on Kudos to say thank you for response from user that is not employed by Dell. Please share an update on progress, so that other users derive benefit from your experience. Thank you. 

If your system has a built-in battery remove the base of the laptop and unplug the battery and remove and reseat the memories in the laptop