Lost access to my WP-Admin File

Hoping someone can help me out

I am having MAJOR problems

My site was hacked about a week ago and Malware installed. I removed the malicious code from my Header.php file but it seems to have made things worse.

I had a WP Developer working on my site for 3 hours and I have lost access to my WP Dashboard.

All I am getting when I try to access the WP-Admin URL is a white screen with one line of text:

Warning: Cannot modify header information – headers already sent by (output started at /home/content/56/4888756/html/wp-content/themes/magazine-basic/functions.php:2) in /home/content/56/4888756/html/wp-includes/pluggable.php on line 876

Have no idea what to do now?? Need some advice on how to fix this

Thanks

Sheryl B

Fashion Development Group