Re: Problem with unknown partition
From fstab it seems you are not using sda5. It might be corrupted or something from earlier (or if you tried manipulating it from windows). It should be safe to delete it but you can't use it for much except to expand sda7 because sda5 physically is after sda7, so you can't expand sda6 to use it for example.
If you decide to delete it, do it from ubuntu not windows.
Darko.
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Ubuntu 18.04 LTS 64bit
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