Ok! Thanks a lot for this information I will start my research alone and I will post in the BIOS section if I need help. :)

Hello !
Sorry, I didn't answer earlier I had some work to do. I did some research by myself and looked for differences between my backup file and the BIOS file. I didn't understand why a whole part was different and I remembered that I tried to switch from A11 bios to A09 bios. So the first part of my backup corresponds to the A09 bios and the other part to A11... The difference starts from line 003B C890.
I will attach the files and screenshots to illustrate my point. Indeed in my backup I find the service tag of my PC and codes, potentially those that are missing for my Windows.

Now I could edit the A11 file to add the missing lines by copying my backup and flashing my bios but I don't know how to do it and I don't know if it's a good idea.

Is it feasible or should I give up?
Thanks in advance !

Difference 1
Difference 2
Difference 3
Difference 4

Thanks for your answer!
I modified my file with VBinDiff (it is really good this software) but I have just 2 places where I don't know what to do.

On the first one I have 00 00 00 00 on the a11 bios and FF FF FF FF on the backup. Should I modify or do I not care?

On the second one I have two lines present on the bios a09 and a11 but absent from the backup. (003A FFE0 & 003A FFF0) Should I delete them ?

And I did not understand how I can test the bios once I'm done, I would need a little more explanation, sorry.

Thanks again for your help!

Ok perfect, I have my file ready. But I don't understand how to flash the bios. I have a USB key with FreeDOS and apparently I have an American Megatrends BIOS, I can't find the program that would allow me to flash it. The only ones I have found ask me for a .ROM file when I have a .bin. I must have missed something somewhere... Sorry if my question is stupid, I'm a bit lost.

Thanks for the information, I was able to move forward !
I can now make a backup of my BIOS, flash the bios with this backup or with the original A11 but as soon as I try to flash with a modified BIOS I get an error: "ERROR Checksum BIOS : bad".
I tried to flash by modifying the backup of my current bios, by modifying the original A11, by modifying just the service tag, by changing just one character... Still the same error. I don't understand how to pass it.
Searching I didn't find anything that could help me. If you have an idea that would be cool.
Sorry to take so much of your time.

So, I bricked the card again haha... I give up, thanks anyway, I learned a lot ! :)