Hello there,
I have read your project description carefully, i have understood the work, you are facing the issue on your magento website 500 internal server error after customer login, can you please provide me your magento website url and FTP and admin login detail so i can check what the problem there, currently i am working magento project, i have 10 + year experienced in IT Company
We are a 10 year old IT company with highly skilled designers and developers to work on php, Mysql, Jquery, Wordpress, OSC, Magento, OpenCart, Mobile development, iPhone, Responsive etc.
It would be better if you come to have a close discussion over chat .
Best Regards
Harpreet Singh