Remove Win-11, new install win-7 PRO

[bawldiggle]

I want to reinstall Win-7 (PRO) 64-bit onto an original Win-7 machine.
The original primary disc (C:\) was an SSD with Win-7 PRO.
The original SSD failed ... or the original Win-7 OS corrupted . . . ??
A local shop installed a new SSD with Win-11 as the OS. . . . . DISASTER

I have purchased (and downloaded) a genuine ISO (file) including licence key from Keysfan.

The target machine was/is a custom build for Win-7 about 4 years ago.

I am 77 ... living on borrowed time (5 years in 2008) and now vision impaired.
Win-11 all white UI is a disaster for me . . .

I am using a Lenovo laptop with a 23inch monitor to get the help I need
​

How do I install Win-7 (ISO) ?
Do I need a new SSD primary drive OR can I overwrite the Win-11 SSD ?
I don't know if the shop-genius has tweaked the BIOS to install Win-11

I do not want dual boot !​

I have a 2016 Mini Tools Bootable disc (64bit) . . . if I need it.​

My brain cells have taken a beating since 2008 and again in 2019 ... so I am not the sharpest knife in the drawer
A step by step how-to would be appreciated​

Thank you I would appreciate any help

 

[SIW2]

Win-11 all white UI is a disaster for me . . .

Have you tried dark mode?

To enable Windows 11 dark mode, open Windows 11 Settings > Personalization > Colors and choose the “Dark” option.

If that does not suit you, then you can install windows 7

can I overwrite the Win-11 SSD

yes

what is the model number and name of the motherboard ?

 

[bawldiggle]

Thank you for your help
CPUz report attached

 

[Megahertz07]

What kind of media (DVD or USB) is your Win 7 installation drive?

You have a Intel Core i5 3470 Ivy Bridge CPU and a GA-B75M-D2V MB.
It's a 2012 computer. At that time Win 7 was the current Windows so your computer is perfect for Win 7.
Boot from a Win 7 installation drive, go to install, delete all partitions on the drive till you have one and only one unallocated space and then proceed.
Make sure you install same version (Home, HP, Pro or ultimate) of the license key you have.

For the updates use Single file with all updates - Simplix