User NAme in full URL for use in redirection

I am trying to create a URL in wordpress/buddypress that calls the logged-in user name within the url so that i can redirect to a different page.

https://www.website.com/members/USER_NAME/profile/notifications

I need the url to insert the logged in users name so that I can redirect them to another page – from the example link above to example below:

https://www.website.com/members/USER_NAME/activities/notifications

Any idea?