Dynamic product parameters in theme app extension

[NemoPS]

Hi everyone,
Just started learning how to code Shopify apps and I am having a real hard time understanding the system.
Right now I need to access product data within my view (theme app extension) and particularly the product stock. 

How would I go about doing that? While I can fetch data from graphql in the mail app with react, the examples don't show anything dynamic for app extensions. Still, I do need to fetch dynamic product data in the frontend block.

Also, if there is any real documentation I am missing, feel free to post it!

Thanks in advance