Warning: Cannot modify header information… and no access to wp-admin

I have run into a Warning: Cannot modify header information… and as a result I cannot access the wp-admin dashboard. The peculiar thing is that I can access all of my website without any error except for 3 subpages:

1- https://synergyptpilates.com/pilates/#schedule
2- https://synergyptpilates.com/pilates/#fees
3- https://synergyptpilates.com/pilates/#cancellation

Here is the complete error message:
Warning: Cannot modify header information – headers already sent by (output started at /home/content/62/11106162/html/Synergy/wp-includes/class-wp-ajax-response.php:1) in /home/content/62/11106162/html/Synergy/wp-includes/pluggable.php on line 1207

Here is pluggable.php line 1207: header(“Location: $location”, true, $status);

Any one can help?