Failed to install pihole and now I don't have internet access

[cipicu]

Hi! I just installed Ubuntu server on a laptop and I have a problem. I used the one step automatic install for pihole and the installation stopped with the error: “dns resolution is currently unavailable”.
I search the net and I found as a solution changing the nameserver to 127.0.0.1 in /etc/resolv.conf file, so I did. I tried again to run the curl but now I have this error: “curl: (6) Could not resolve host: install.pi-hole.net”.
In addition, I can’t access the internet with that laptop. I can access the internet with other devices using WIFI.
I changed the nameserver to 1.1.1.1, 8.8.8.8, 9.9.9.9. No change!
I can ping 8.8.8.8 but no google.com. Has anyone an idea?
Regards

[jfb]

Please upload a debug log and post just the token that is generated after the log is uploaded by running the following command from the Pi-hole host terminal:

pihole -d

or do it through the Web interface:

Tools > Generate Debug Log

[cipicu]

~$ pihole -d

Command 'pihole' not found, did you mean:

command 'pahole' from deb dwarves (1.15-2)

Try: sudo apt install

On the first screen after I login using putty:

5 updates can be applied immediately.
5 of these updates are standard security updates.
To see these additional updates run: apt list --upgradable

Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings

I tried to do an update and this is the result:
~$ sudo apt update
Err:1 Index of /ubuntu focal InRelease
Temporary failure resolving 'ro.archive.ubuntu.com'
Err:2 Index of /ubuntu focal-security InRelease
Temporary failure resolving 'security.ubuntu.com'
Err:3 Index of /ubuntu focal-updates InRelease
Temporary failure resolving 'ro.archive.ubuntu.com'
Err:4 Index of /ubuntu focal-backports InRelease
Temporary failure resolving 'ro.archive.ubuntu.com'
Err:5 Index of /ubuntu focal-security InRelease
Temporary failure resolving 'ro.archive.ubuntu.com'
Reading package lists... Done
Building dependency tree
Reading state information... Done
5 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: Failed to fetch http://ro.archive.ubuntu.com/ubuntu/dists/focal/InRelease Temporary failure resolving 'ro.archive.ubuntu.com'
W: Failed to fetch http://ro.archive.ubuntu.com/ubuntu/dists/focal-updates/InRelease Temporary failure resolving 'ro.archive.ubuntu.com'
W: Failed to fetch http://ro.archive.ubuntu.com/ubuntu/dists/focal-backports/InRelease Temporary failure resolving 'ro.archive.ubuntu.com'
W: Failed to fetch http://ro.archive.ubuntu.com/ubuntu/dists/focal-security/InRelease Temporary failure resolving 'ro.archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/focal-security/InRelease Temporary failure resolving 'security.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.