I am new with ubuntu

few days ago I changed my dns like this :

sudo /etc/resolv.conf

and after adding two new DNS I saved it

now I wanna to get it back to the default

but when I open the resolv.conf

I see this :

# This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
# Do not edit.
#
# This file might be symlinked as /etc/resolv.conf. If you're looking at
# /etc/resolv.conf and seeing this text, you have followed the symlink.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0 trust-ad
search .
~                                                                                                                                                                                                                  
~                                                                                                                                                                                                                  
~ 

and it seems nothing has changed

but I know that DNS has changed and I can see it’s effects .

so , How can I get it back to default ?