This is a four character phrase for which I have found no accurate translation online. I hear it all the time around CNY.
万事大吉
This is an expression wishing the listener good luck. Any equivalent English expression will do: "Best of luck in all your endeavors", "May your every endeavor prosper", etc. The use of the character 万 (wàn, meaning "10,000"), here just means "many" or "all".
If you get PeraPeraKun plugin (avail for Chrome and FireFox) it gives you the meanings of all of these idioms on hover.

grep.
– Becky 李蓓
Mar 12 '20 at 23:30
A idiomatic usage to show you hope everyone will be fine or send a congratulation messages to others when Lunar New Year come. It often comes like "祝各位新的一年心想事成,万事大吉"
It's congratulatory speech.