Wordpress Website customization

Kindly visit [login to view URL] and learn about the website. It uses a custom theme which needs to be further modified. There is a challenge option on the website (available when you are registered as a team and visit another team's page). When you issue a challenge to another team you need to fill a simple form. The form needs customization and a payment method needs to be hooked based on a rule-set. Further the challenge option itself needs to be customized. Currently it is a 1-1 challenge but it is required to a 1-many challenge from the user's team page itself. This challenge needs to be published on a separate page as a list. The challenge details form will be same as above. The above form also needs to be integrated with a scheduling feature (free plugins can be made use of) that will take care of date and time-slot. This needs to be linked with server instance (block an instance for the schedule chosen if our servers are chosen or simply provide a date and time stamp for other users to see if user chooses his/her own server.