SHAKOOR wrote: ↑
Tue Feb 12, 2019 6:43 am
SQL ERROR [ mysqli ]
Disk full (/tmp/#sql_1a8_6.MAI); waiting for someone to free some space... (errno: 28 "No space left on device") 
As per david63, get the necessary info from your host.
A temporary solution would be to remove old and redundant errorlogs from your server, also remove too old backups you may have, reduce your database size by optimising it (you may have to free up some space first, e.g. by truncating the search tables (and later restoring or repopulating).