Are these errors serious?

Not really. It means your BIOS is reporting things the kernel does not understand. Often ACPI related and probably no working hibernation/suspend. I used to have them too but my ssd is so quick I nowadays do not bother with hibernation/suspend anymore.

How can I fix them?

See the first line: contact your BIOS vendor for fixes. A BIOS update can fix this. The second option would be to report these against the kernel used if this has not happened already (probably is ;) ) and wait for a fix.