Google Tag Manager Fixing undefined Variables

Hello,

I need urgent help from someone who knows how to work fast immidiatly on undefiened Data which we get inside the Variables in Google Tag Manager.

for Example:

My Data Layer Looks like This:

{
event: "view_item",
gtm: {uniqueEventId: 297, start: 1701096179133},
ecommerce: {
currency: "EUR",
value: 2799,
items: [
{
item_id: "2345",
item_name: "xxxxxxxx",
affiliation: "xxxxx",
coupon: "lorem233",
discount: 400,
index: 0,
item_brand: "lorem ipsum",
item_category: "lorem ipsum",
item_category2: "Japan",
item_category3: "Reisejahr 24",
item_variant: "",
price: 3199,
quantity: 1
}
]
}
}

but if i use ecommerce.items.0.items_id i get undefined back.
I need that on several other undefined variables.

Start should be immidiatly since its urgent.