Hi Nadim,
The best thing here is to first of all read over:
That will give you the foundation you need to make changes safely 🙂
The basic idea though would be to override the single events template with your own custom events/single.php template. The code that pulls in the ticket form looks like this:
<?php if (function_exists('tribe_get_ticket_form') && tribe_get_ticket_form()) { tribe_get_ticket_form(); } ?>
You can reposition it to suit your needs – does that help?