8 Go de RAM (5,88 Go utilisables)

I would like to have the 8GB!

Hello
your 2GB of RAM is reserved by your "AMD Radeon Vega Mobile" graphics chip.
On computers with an integrated graphics card, part of the RAM is generally dedicated to the operation of the video card. The rest of the RAM remains available for the operation of the computer. This could explain the difference. To check, click on Start > Settings > System > Display. In the left part, at the bottom, click on Advanced display settings. In the page that opens, at the bottom click on Video card properties for the display. In the next window, the size of the memory dedicated to the video card is clearly indicated. In the case of a video card included in the motherboard, this size is deducted from the RAM. The rest corresponds to the memory available for the computer.

Ah, that's why it's AMD 2GB video
But still. I have a GTX 1650 4GB

If I use my GTX 1650 instead, is it the same?

If in your BIOS you don't have a video memory setting, you can't do anything.

My BIOS is up to date:
BIOS Version/Date AMI F.08, 09/07/2020