Nostr and bitcoin can be frustrating, there’s lots to learn. Hashtags allow you to categorize your notes for other users. I for example follow some hashtags and see when someone posts a note with said hashtag (whether I’m following them or not).

To reply to a post on Damus, go to the bottom of the note and look for the button to reply next to repost and zap button.

Hang in there, welcome to nostr and endless rabbit holes.