I am new to this community. Recently I bought a new laptop and decided to install Ubuntu on it. Everything worked fine for a few days, but since yesterday Ubuntu keeps freezing for apparently no reason. When that happens, nothing will work. It's all frozen and I have to turn it off with the power button. I have no good knowledge about Linux in general, so I don't know how to approach this problem.
Occasions: The freezes happened so far when I was having Firefox and Visual Studio Code open.
Here is a piece of the system log, if someone can take a look at it.
May 4 22:45:56 milan-X551MA systemd-timesyncd[583]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com).
May 4 22:45:57 milan-X551MA systemd-timesyncd[583]: Synchronized to time server 91.189.94.4:123 (ntp.ubuntu.com).
May 4 22:46:05 milan-X551MA systemd[1]: Starting Stop ureadahead data collection...
May 4 22:46:05 milan-X551MA systemd[1]: Started Stop ureadahead data collection.
May 4 22:46:05 milan-X551MA systemd[1]: Stopped Read required files in advance.
May 4 22:47:22 milan-X551MA systemd[1]: Stopping User Manager for UID 108...
May 4 22:47:22 milan-X551MA systemd[934]: Reached target Shutdown.
May 4 22:47:22 milan-X551MA systemd[934]: Starting Exit the Session...
May 4 22:47:22 milan-X551MA systemd[934]: Stopped target Default.
May 4 22:47:22 milan-X551MA systemd[934]: Stopped target Basic System.
May 4 22:47:22 milan-X551MA systemd[934]: Stopped target Sockets.
May 4 22:47:22 milan-X551MA systemd[934]: Stopped target Paths.
May 4 22:47:22 milan-X551MA systemd[934]: Stopped target Timers.
May 4 22:47:22 milan-X551MA systemd[934]: Received SIGRTMIN+24 from PID 1930 (kill).
May 4 22:47:22 milan-X551MA systemd[1]: Stopped User Manager for UID 108.
May 4 22:47:22 milan-X551MA systemd[1]: Removed slice User Slice of lightdm.
May 4 23:00:00 milan-X551MA systemd[1]: Starting Cleanup of Temporary Directories...
May 4 23:00:00 milan-X551MA systemd-tmpfiles[2027]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
May 4 23:00:00 milan-X551MA systemd[1]: Started Cleanup of Temporary Directories.
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May 6 11:43:50 milan-X551MA AptDaemon.Worker: INFO: Finished transaction /org/debian/apt/transaction/12ad1d59834e4f6283f4d124a44f0e5d
May 6 11:43:50 milan-X551MA org.debian.apt[718]: /usr/lib/python3/dist-packages/aptdaemon/progress.py:491: Warning: Source ID 34 was not found when attempting to remove it
May 6 11:43:50 milan-X551MA org.debian.apt[718]: GLib.source_remove(id)
May 6 11:43:50 milan-X551MA org.debian.apt[718]: /usr/lib/python3/dist-packages/aptdaemon/progress.py:491: Warning: Source ID 35 was not found when attempting to remove it
May 6 11:43:50 milan-X551MA org.debian.apt[718]: GLib.source_remove(id)
May 6 11:43:50 milan-X551MA org.debian.apt[718]: 11:43:50 AptDaemon.Worker [INFO]: Finished transaction /org/debian/apt/transaction/12ad1d59834e4f6283f4d124a44f0e5d
May 6 11:43:52 milan-X551MA gnome-session[1487]: (gnome-software:1612): Gs-WARNING **: Failed to create permission org.freedesktop.packagekit.trigger-offline-update: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Action org.freedesktop.packagekit.trigger-offline-update is not registered
May 6 11:43:58 milan-X551MA gnome-session[1487]: message repeated 2 times: [ (gnome-software:1612): Gs-WARNING **: Failed to create permission org.freedesktop.packagekit.trigger-offline-update: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Action org.freedesktop.packagekit.trigger-offline-update is not registered]
May 6 11:44:03 milan-X551MA systemd[1]: Stopping User Manager for UID 108...
May 6 11:44:03 milan-X551MA systemd[930]: Stopped target Default.
May 6 11:44:03 milan-X551MA systemd[930]: Stopped target Basic System.
May 6 11:44:03 milan-X551MA systemd[930]: Stopped target Paths.
May 6 11:44:03 milan-X551MA systemd[930]: Stopped target Timers.
May 6 11:44:03 milan-X551MA systemd[930]: Stopped target Sockets.
May 6 11:44:03 milan-X551MA systemd[930]: Reached target Shutdown.
May 6 11:44:03 milan-X551MA systemd[930]: Starting Exit the Session...
May 6 11:44:03 milan-X551MA systemd[930]: Received SIGRTMIN+24 from PID 2467 (kill).
May 6 11:44:03 milan-X551MA systemd[1]: Stopped User Manager for UID 108.
May 6 11:44:03 milan-X551MA systemd[1]: Removed slice User Slice of lightdm.
May 6 11:45:38 milan-X551MA wpa_supplicant[915]: wlp2s0: CTRL-EVENT-REGDOM-CHANGE init=BEACON_HINT type=UNKNOWN
May 6 11:54:29 milan-X551MA AptDaemon: INFO: Quitting due to inactivity
May 6 11:54:29 milan-X551MA AptDaemon: INFO: Quitting was requested
May 6 11:54:29 milan-X551MA org.debian.apt[718]: 11:54:29 AptDaemon [INFO]: Quitting due to inactivity
May 6 11:54:29 milan-X551MA org.debian.apt[718]: 11:54:29 AptDaemon [INFO]: Quitting was requested
May 6 11:56:09 milan-X551MA com.canonical.Unity.Scope.Applications[1351]: Error loading package indexes: Couldn't stat '/var/cache/software-center/xapian'
May 6 11:56:09 milan-X551MA com.canonical.Unity.Scope.Applications[1351]: (unity-scope-loader:2808): unity-applications-daemon-CRITICAL **: daemon.vala:144: Failed to load Software Center index. 'Apps Available for Download' will not be listed
May 6 11:56:10 milan-X551MA com.canonical.Unity.Scope.Music[1351]: (unity-music-daemon:2812): unity-music-daemon-WARNING **: rhythmbox-collection.vala:510: Unable to open album-art DB!
May 6 11:56:10 milan-X551MA com.canonical.Unity.Scope.Music[1351]: (unity-music-daemon:2812): unity-music-daemon-WARNING **: rhythmbox-collection.vala:574: Error while parsing rhythmbox DB: Error opening file: No such file or directory
May 6 11:57:13 milan-X551MA systemd[1]: Starting Cleanup of Temporary Directories...
May 6 11:57:13 milan-X551MA systemd-tmpfiles[2897]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
May 6 11:57:14 milan-X551MA systemd[1]: Started Cleanup of Temporary Directories.
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May 6 12:04:23 milan-X551MA kernel: [ 1391.428585] perf interrupt took too long (2528 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
May 6 12:08:10 milan-X551MA org.gnome.zeitgeist.SimpleIndexer[1351]: ** (zeitgeist-fts:1838): WARNING **: Unable to get info on application://nautilus-autostart.desktop
May 6 12:09:39 milan-X551MA dbus[718]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service'
May 6 12:09:39 milan-X551MA systemd[1]: Starting Hostname Service...
May 6 12:09:39 milan-X551MA dbus[718]: [system] Successfully activated service 'org.freedesktop.hostname1'
May 6 12:09:39 milan-X551MA systemd[1]: Started Hostname Service.
May 6 12:09:40 milan-X551MA org.gtk.vfs.Daemon[1351]: ** (process:3010): WARNING **: Couldn't create directory monitor on smb://x-gnome-default-workgroup/. Error: Operation not supported by backend
May 6 12:10:20 milan-X551MA org.gtk.vfs.Daemon[1351]: ** (process:3004): WARNING **: Couldn't create directory monitor on smb://x-gnome-default-workgroup/. Error: Operation not supported by backend
May 6 12:15:49 milan-X551MA rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="737" x-info="http://www.rsyslog.com"] start
May 6 12:15:49 milan-X551MA systemd-modules-load[257]: Inserted module 'lp'
May 6 12:15:49 milan-X551MA systemd-modules-load[257]: Inserted module 'ppdev'
May 6 12:15:49 milan-X551MA rsyslogd-2222: command 'KLogPermitNonKernelFacility' is currently not permitted - did you already set it via a RainerScript command (v6+ config)? [v8.16.0 try http://www.rsyslog.com/e/2222 ]
May 6 12:15:49 milan-X551MA rsyslogd: rsyslogd's groupid changed to 108
May 6 12:15:49 milan-X551MA rsyslogd: rsyslogd's userid changed to 104
May 6 12:15:49 milan-X551MA systemd-modules-load[257]: Inserted module 'parport_pc'
May 6 12:15:49 milan-X551MA systemd[1]: Started Load Kernel Modules.
May 6 12:15:49 milan-X551MA systemd[1]: Starting Apply Kernel Variables...
May 6 12:15:49 milan-X551MA systemd[1]: Mounting FUSE Control File System...
May 6 12:15:49 milan-X551MA systemd[1]: Mounted FUSE Control File System.
May 6 12:15:49 milan-X551MA systemd[1]: Started Create Static Device Nodes in /dev.
May 6 12:15:49 milan-X551MA systemd[1]: Starting udev Kernel Device Manager...
May 6 12:15:49 milan-X551MA systemd[1]: Started Apply Kernel Variables.
May 6 12:15:49 milan-X551MA systemd[1]: Started Braille Device Support.
May 6 12:15:49 milan-X551MA systemd[1]: Started LVM2 metadata daemon.
