Your macOS drive is a mess, the system seems to idle and the fan tends to panic more than reason? Your TimeMachine backup no longer ends?
You went to High Sierra and converted your disk to APFS?
Start in “Repair” mode (Command + “R” all the way through the boot phase), run the disk parser on your hard disk and it is likely that you get the following error:
snap_metadata_val object (oid <aléatoire>): invalid extentref_tree_oid (0x0)
Snapshot metadata tree is invalid
To repair that, follow this guide :
Restart your system normally and in a terminal prompt, list the snapshots created :
$ tmutil listlocalsnapshots / com.apple.TimeMachine.2018-03-20-112749 (dataless) com.apple.TimeMachine.2018-03-21-174756 com.apple.TimeMachine.2018-03-22-074442
If the list shows a dataless snapshot like above, delete it:
$ tmutil deletelocalsnapshots 2018-03-20-112749 Deleted local snapshot '2018-03-20-112749'
and the problem is solved !