Hi!

My Debian Linux doesn't get on the internet, but it can ping the internet provider's gateway 192.168.0.1.

I found that the settings in /etc/resolv.conf was wrong:
nameserver 193.216.69.12
nameserver 193.216.1.12

I changed it to what it should be, and saved it as root:
nameserver 193.216.69.10
nameserver 193.216.1.10

When I run "/etc/init.d/networking restart" the numbers change back to 193.216.69.12 and 193.216.1.12.

Question 1: How do I change the nameserver IP?

Question 2: Are there other possible reasons why I don't get on the internet? I did before...

I am afraid you cant change it except if you did a new installation.
Even if you happen to do it your machine will became very slow

I think your problem may depends on resolvconf package. I mean, resolvconf change /etc/resolv.conf behind your back.

Check whether resolvconf installed on your system, try to remove package, or properly configure it.

And, do you use dhcp to assign IP from provider?