error: headers already sent by –> white screen

Hi,

I have a white screen.
I was in the process of adding code for ‘tab with CSS, without jquery’ in twentyfourteenchild theme.

I am facing a white screen.

This error
error_log keeps showing:

Cannot modify header information - headers already sent by
- - - -  (output started at /home/mydoctor/public_html/wp-content/themes/twentyfourteenchild/functions.php:1) in /home/mydoctor/public_html/wp-includes/feed-rss2.php on line 8

Similarly with
_ _ /pluggable.php
__ _ feed-rss2.php
with this error:

Request-URI Too Large
The requested URL's length exceeds the capacity limit for this server.

has now ended with white screen.

I followed the instructions on codex and valuable tips on the support forums, but I am not able to recover my website.
Technical server support hasn’t contributed giving the idea that it is not server related.

What I have?
Freshly installed
WordPress folders
wp-admin
wp-include
wp-config.php
.htaccess
functions.php
twentyfourteen theme.

Respective .php files do not show any error.
.htaccess has minimum default code
wp-config.php has ‘WP_DBUG’ set as true.
but nothing is printing out.
‘WP_DEBUG’, true );
‘WP_DEBUG_LOG’, true );
‘WP_DEBUG_DISPLAY’, true
haven’t shown any thing. I am not too sure where to find debug.php file or debug results.

Thanks in advance for your support.
Dr. Ashok Koparday