How to hide columns in numbers.

try this online help guide by apple.

https://help.apple.com/numbers/mac/4.3/#/tan504013a74

Jason

Have you clicked the little down-facing triangle at the top of a column? If that is not an option I imagine the problem lies in the translation from Excel to Numbers. The translation process is not perfect & if the original Excel file is complex the more likely the translation will have problems.