Very Long Boot Time On My Ubuntu

Question

I'm having a problem with my boot time on Ubuntu. It got unusually long. At first it was very fast, but now it is taking a really long time.

This is my Critical Chain: The time when unit became active or started is printed after the "@" char> The time the unit took to start is printed after the "+" character.

graphical.target @19.608s
└─multi-user.target @19.607s
  └─plymouth-quit-wait.service @10.827s +8.776s
    └─systemd-user-sessions.service @10.788s +15ms
      └─network.target @10.769s
        └─NetworkManager.service @9.233s +1.535s
          └─dbus.service @9.130s +86ms
            └─basic.target @9.026s
              └─sockets.target @9.026s
                └─snapd.socket @9.008s +18ms
                  └─sysinit.target @8.993s
                    └─snapd.apparmor.service @4.025s +4.968s
                      └─apparmor.service @1.599s +2.401s
                        └─local-fs.target @1.596s
                          └─run-snapd-ns-snapd\x2ddesktop\x2dintegration.>
                            └─run-snapd-ns.mount @13.416s
                              └─local-fs-pre.target @629ms
                                └─keyboard-setup.service @497ms +132ms
                                  └─systemd-journald.socket @478ms
                                    └─-.mount @426ms
                                      └─-.slice @426ms
...skipping...
└─multi-user.target @19.607s
  └─plymouth-quit-wait.service @10.827s +8.776s
    └─systemd-user-sessions.service @10.788s +15ms
      └─network.target @10.769s
        └─NetworkManager.service @9.233s +1.535s
          └─dbus.service @9.130s +86ms
            └─basic.target @9.026s
              └─sockets.target @9.026s
                └─snapd.socket @9.008s +18ms
                  └─sysinit.target @8.993s
                    └─snapd.apparmor.service @4.025s +4.968s
                      └─apparmor.service @1.599s +2.401s
                        └─local-fs.target @1.596s
                          └─run-snapd-ns-snapd\x2ddesktop\x2dintegration.>
                            └─run-snapd-ns.mount @13.416s
                              └─local-fs-pre.target @629ms
                                └─keyboard-setup.service @497ms +132ms
                                  └─systemd-journald.socket @478ms
                                    └─-.mount @426ms
                                      └─-.slice @426ms

When it finnaly boots up I enter my password and then appears the "timed out for waiting the udev queue being empty" on red on the top left side of the screen but then it opens the OS normally.