Hardware reserved RAM problem on Aspire E5-533-1786

Ugueust67s

Hello , I switched to Linux (Debian 12 Bookworm) a while ago. As I am a programmer I need a lot of RAM for compilations, recently (about a week ago) I updated Debian 12 to it's latest version. I discovered a "secret" mode in the BIOS, selected "External Graphics" option which freed up the 16GiB of RAM, when I updated Debian I realized that I only had access to 7.2GiB of RAM, Does anyone know how I can free up the 16GiB again?

(When I boot on memtest86 only 7.4GiB can be tested)

***Specifications***

OS: Debian 12 Bookworm (Linux 8.6.0-37)

BIOS Versión: 1.31 , InsydeH20 rev5.0

CPU/GPU: AMD A12-9700P Radeon R7

Laptop model: Aspire E15 (E5-533-1786)

Ugueust67s

Here are some images: (Correction: I have Linux 6.8.0-38-amd64)