By selecting the hamburger menu and then going to Settings > Folders, you may categorise your chats into multiple labels. Now select Create New Folder and give it a name (Personal, Work, Family, etc). Then, in the newly formed folders, you may add the necessary chats.
Simply press and hold the message you want to edit, then tap the pencil icon on the top bar of the screen to change it.
Even if the recipient hasn't turned on Do Not Disturb, messages will not create any sound or vibration. Simply compose your message, hold down the send button, and then select Send silently!
To add nearby users or groups, go to Contacts under the Telegram hamburger menu. Now press the 'Find People Nearby' button. You'll now see a list of Telegram users in your area, as well as groups in the area.