free shipping if pay on pickup

Hey guys,

i need free shipping if pay on pickup.
I rename the normal cheque payment and use it for local pick up.

I find this, but it isn’t exactly what i need:
https://www.xadapter.com/2016/06/15/woocommerce-2-6-hide-shipping-methods-when-free-shipping-is-available/

Do you have a small code snippet for the funtctions.php oder a plugin?

Thanks
Florian