I have tried to warn everyone about the upgrade issues. For most people it has gone ok, with only minor issues. For other wordpress websites, it has been a disaster.
2) the database needs to be at least mySQLi or Maria DB.
3) you have to check the theme and make sure it is compatible with 5.0 and PHP7.2+
4) you have to check all the plugins and make sure they are compatible with 5.0 and PHP7.2+
5) you have to check the theme and make sure it is compatible with 5.0 and PHP7.2+
This is not your normal upgrade as the hosting environment needs to change to support the new Wordpress 5.0+ version. So..., long story short, managed hosting with automatic upgrades are crashing websites.
Call Us If You Are Having Any Issues At All