HELP with unknown edit to function.php

Someone help!

I was in my funtion.php editor and was trying to install footer widgets but something happened while I was inside it and it is now giving me the error:

Warning: Cannot modify header information – headers already sent by (output started at /home/content/88/11422788/html/wp-content/themes/money/functions.php:277) in /home/content/88/11422788/html/wp-includes/pluggable.php on line 1121

when I try to do anything – update a page, etc. The warning was showing on the live site. I removed my pop up widget and that removed it, but now I’m getting this error when I update anything. I’d also like to have my pop up back!

How can I fix this? The website is https://www.makingyourownmoney.com.

THANK YOU!