You are asking strangers who have no idea what’s wrong with your code instead of debugging it.
First of all you have to narrow the problem to the smallest code possible, means there should be no input, no POST, no pakket_items_wijzigen, no pakketten but just a hardcoded array of values and a code to update.
I’ll give you where you are going wrong, but it’s up to you to fix it.
names=“items” in your input tag should be something like names=“items[index_name]” that is the reason you are only getting the last item, for you only have one index. Let me state I am just guessing I could be wrong, but that’s where I would start debugging at.