Hello Hannah!
You will need to create a new entity to store the information, Item_Approver for example. In this entity you can store a join to the item, to the approver user, the approval status, date, and other information that you need. Then, as soon as someone signs, you can search if someone hasn't signed yet, if you can't find it, you can update the status in your item entity.
This way, you can have complete control of who signed and when, also serving as a history.
I think you can also make us of a very easy workflow that handles the tasks for you:
As for the viewing part: