Yea, so admittedly this is conceptually different than when you're dealing with a traditional social media app that effectively uses 1 "relay" owned and controlled by the same people that create the app. They can say "hey when you click delete we promise we'll delete it" (although that's a shallow promise also, they keep everything, they just are saying they won't show it to other users")

Which app are you using?  Some apps and relays do support "deletion requests" and post edits. 

"Deletion requests" are called deletion *requests* because the app can't force all relays to delete your post. The app author and relay owner are different parties. A "request" is the best the app can do. 

Edits are somewhat similar. When you edit a post on Nostr you're really creating a new post and the apps just understand how to replace the old with the new when they pull the posts down from the relays. But the ability to do this is up to the app.  

 I use Primal. Not sure what else an app/application can be on a pc(sorry, really a bit of a tech dinosaur with computer language)
I do understand relay a bit better now, thank you. 
I did click on most relays offered in the settings and my newsfeed seems to be getting somewhat more diverse in content, maybe also as I follow more people.. So if I would like to get content on lets say 'knowledge of editable plants and their health benefits' or 'how to prepare and cook chicken properly'so it aint dry', is there a relay for that?, and where do I find that? 🙏