Undefined variable when trying to run bin/watch-storefront.sh

Beforehand let me say that i am new to shopware, and do not understand the system completely yet.
I have a wish to run bin/watch-storefront.sh to use the hot-reload functionality. This is for the purpose to see the changes while happening.
When trying to run watch-storefront.sh it cannot understand some variables defined by shopware itself.

My OS is Ubuntu 20.04.2 LTS
Hardware is:
Ram: 32GB DDR4
Motherboard: PULSE1501 Tuxedo Computer
CPU: AMD Ryzen 7 4800H with Radeon Graphics

If there is any more information you need, then i will gladly provide it.

Thank you very much beforehand

You may also watch it in bash playback Run the init command in a directory where you want to install Vue Storefront 2 minutes ago NomNom Dog Food Up 2 minutes vuestorefront_app_1 as in host: container; environment allows you to add enviroment variables.