Mojave upgrade isue

Installed Mojave on a 2009 Mac Pro 4.1 firmware update to 5.1. The installation appeared to go fine and I have been using it for the past couple of days no problems. However today I rebooted my machine and

1) I get the Mojave background and all the icons in the dock seem larger than usual (is this Mac safe mode?).

2) it says that Mac OS needs to repair applications. However whenever I enter my password (the one I use to log in and make changes) it doesn’t recognise it. I’m now stuck in a loop. Any suggestions? Thanks.