It looks like the version of Libre office you try to install cannot work together with the version of Open Office you have. Try to boot into the recovery mode and fix broken packages from there. To achieve this, choose Advanced options for Elementary OS from the grub bootmenu screen, then Recovery mode. Connect to the network from there first, and after ...
As the log says, it may have been because the mirror was stuck while syncing. If you run your original sudo apt update command it should now be fine.
If an error still occurs, you can try removing the apt cache with the following command:
sudo rm -r /var/cache/apt/* /var/lib/apt/lists/*
That is because of cached metadata. Executing the following command on terminal will delete your cached metadata and re-download them,
sudo rm -rf /var/lib/apt/lists/* sudo apt-get update sudo apt-get clean
And I suggested sudo apt-get install --fix-missing on comment as a bonus to install / fix any broken package, but this was not necessary for your ...
After executing sudo apt update I see this line in terminal's output:
http://packages.elementary.io/appcenter bionic InRelease
http://packages.elementary.io/appcenter juno Release
As my system doesn't have any issues with updates, you could try to swap the lines and see if it helps. (If it doesn't, just revert the process and try other ...
VLC uses libav (also backend to ffmpeg), which can decode just about any type of digital audio or video format.
I think Videos is using gstreamer, which needs individual codecs to handle each format. Most of these come in the packages gstreamer-plugins-good, gstreamer-plugins-bad, and gstreamer-plugins-ugly.
Installing those three should cover most ...