I try many different options, included posted on this forum,
I've always get a ERROR Unable to build NVIDIA kernel module.
I'm using the 64 bit version. This is my Video card, thanks a lot.
5.7.0-0.bpo.2-amd64
Graphics:
Device-1: NVIDIA GT200 [GeForce GTX 260] driver: nouveau v: kernel
bus ID: 01:00.0
Display: x11 server: X.Org 1.20.4 driver: modesetting unloaded: fbdev,vesa
resolution: 1440x900~60Hz, 1280x1024~60Hz
OpenGL: renderer: NVA0 v: 3.3 Mesa 18.3.6 direct render: Yes
Well, the nouveau driver is not too bad, but if you coldn't find another solution yet -
try this: (backup important data/settings before ! )
Use at your own risc 
(Info: This is "nvinvidia-detect" )
apt-get install linux-headers-$(uname -r|sed 's,[^-]-[^-]-,,') nvidia-legacy-390nouveaunouveauxx-driver
sudo apt install nvidia-settings-legacy-390xx
(add contrib and non-free to sources via synaptic)
sign in as root
In Terminal:
apt-get update
apt-get install nvidia-detect
nvidia-detect (to identify your Nvidia GPU and verify required driver package)
dpkg --add-architecture i386
apt-get install libavcodec-extra
apt-get invinvidia-detect
apt-get install linux-headers-$(uname -r|sed 's,[^-]-[^-]-,,') nvidia-legacy-390nouveaunouveauxx-driver
sudo apt install nvidia-settings-legacy-390xx
have fun 