add service fee

I have one plugin that adds a fee based on payment gateway and a 3dplugin that adds a startup cost as a fee

i then added this plugin to add a service fee before the cart total

from the start it only used the cart total to calculate the fee but i managed to change line 150 in woocommerce-service-fee.php to read

$total = ($woocommerce->cart->subtotal + $woocommerce->cart->shipping_total ) ;

so no at least it does calculate the fee based on those 2 numbers

Subtotal 32 DKK
Shipping
Bring – Hjemmelevering (17-21): 122 DKK
Bring – Pakkeshop: 48 DKK
GLS – Omdeling til erhverv: 58 DKK
GLS – Omdeling til privat: 74 DKK
GLS – Til PakkeShop: 52 DKK
PostNord – Erhvervspakke: 60 DKK
PostNord – MyPack Home: 80 DKK
PostNord – MyPack Collect: 58 DKK
Startup Cost 50 DKK
Service Fee 15 DKK
Håndtering 8 DKK
Total 227 DKK`

all 3 fees before the cart total does make use of the add fee function so i’m lost on how to figure out things