Downgrade Windows 10 to Windows 7?

I want to play Windows 7 on my laptop again using a DVD, as there's no working graphics driver for Windows 10.

Can data be lost with something like that or does all of this remain?

With such a downgrade you have to do a new installation. So save all data beforehand! No data is automatically transferred.

Enter in the BIOS start with DVD.

Erase and reformat all disks beforehand.

Back up all important data beforehand.

The PC is then in the delivery state.

I would not do that.

Drivers can also be downloaded later from Win.