I am new to SP online.
This is about a lookup column that displays data from another list which is currently exceeds the 5000 items limit?
Any easy solution as I dont have much programming experience.
This will never work, you are pretty much out of luck.
I have been down this road and still travelling along it. Once SharePoint hits 5k anything, it falls over in almost every sense of the word.
SharePoint Online is not meant for enterprise use, period.