Clear android internal memory

[NerdBotBot]

Hi,

I have a Moto G4 Plus (16 GB). Usable memory is around is 11 GB. After downloading a 9 GB of mkv files, I moved them to my PC. However, 2.5 GB in the internal memory is still occupied.

I deleted every folder, used apps like Master Clean & CCleaner. Nothing worked.

So, any idea how I can clear the internal memory?

 

[Dannydet]

That's part of the system files, which is the OS. Can't be removed