What did Jesus do and where did He go during the three daysand nights in the heart of the earth after His death?

Answer:
During the 3 days in the grave, He went to “paradise” as it was known in the Old Testament. All of the saints from the OT were there, and their spirits had yet to be released to go to Heaven. I am attaching an image that shows how the “underworld” was divided up and is today. Today paradise is empty because all saints go directly to Heaven upon their death.