Sorry but i didn’t get the part “create a new directory to hold the Nvidia package sources and change into it”
Where i should put that folder, and what should be the exact name of that folder. I simply created a folder named NVIDIA to the home folder.
I managed to reach this step:

user@userpc:~$ sudo dpkg -i nvidia-current-updates_*.deb
dpkg: error processing nvidia-current-updates_*.deb (–install):
cannot access archive: No such file or directory
Errors were encountered while processing:
nvidia-current-updates_*.deb

Thanks for any help!