Passing simple text/date data between screens in a Canvas power app

Apologies if this has already been covered, it really annoys me when someone lazily adds a query without checking existing posts and/or a good google first (i offer help on another forum for my area of expertise so am hoping for some positive karma!) however having genuinely spent over an hour searching, including reading several posts on here and other sites and also a few youtube videos i can't find the answer - i suspect my app may be too basic and not what Powerapps was designed for but I'm hoping i can make it work.

I have a main screen which lists 4 items (TG1-TG4) with each having a button linking to a dedicated screen for each (which i have linked without issue using the navigate function). Still on this main screen there is a simple list below showing 'issued to' and 'until' for each. Hopefully i have pasted an image below:

Clicking on the buttons links to a matching screen for each number as below (if i have pasted the screen shot correctly) i am trying to get the information the user enters into these boxes transferred automatically onto the main screen above to populate the matching boxes but don't know how to - i have tried variations of examples i have seen but can't get any to work?

I have done a lot of reading and trial and error as well as youtube watching and understand the basics re updating/naming the labels etc (and have done so) but would really appreciate some help achieving the above.

Only the current information (i.e. who has them) is needed and once over typed with the next persons details the old info isn't needed, i don't need databases or anything else.

(i have set the click to submit button to take the user back to the main page, where hopefully the details will have updated)