If you are using the BP-Default theme you just go into your WordPress Admin panel, go to Themes, choose “Editor” and you should then be able to find what you are looking for in BuddyPress Default under;
Main Index Template
(groups/index.php)
This file should be where you can rename those few things, among others, though you really should create a child theme (https://codex.buddypress.org/theme-development/building-a-buddypress-child-theme/) to add any such changes or customizations with in order to future-proof yourself so that when a new version of BuddyPress is released it doesn’t overwrite your own custom changes to the code.
Don’t forget to save the changes to the file before you proceed, and be extra careful as to what you are making any such changes to when doing so!
If you mess it up you can always pull a fresh file from another copy of BP-Default and upload it to the correct place on your server and just start over from scratch.
Good luck!
The best way is to create a language file to change all instances
