Doubt ban

I was banned from cs go, if I buy the game again on the same account can retrieve items?

You don't have an option to buy it on the same account if you already have it in your library, but you could try and trade your stuff to a friend and then get him to trade your new account... maybe

Not if you are VAC Banned, then your items will be trapped on that account for cs go

If you're banned you don't get the items back, for example if you were vac banned on CS:GO on that account your CS:GO items disappear apart from your trading cards.