how to retrive particular event and make a player to register for it and changing the count
As I am using the Template gird here while clicking on the particular register button it is not taking directly particular event for the player to register.it asking to choose the events and how to increase the total no.of registrations as the player register for a particular event and the available seats value has to be reduced.
You say you're using a “create object” button, but for your use case it might be better to use a microflow. This way you can use the event as an input parameter for your microflow, and use it to immediately set the association of the “Registration” object to the correct event. You can still open a detail page after that with an open page action if you want the user to be able to fill out more details. In the microflow, you will also be able to increase the number of registrations to the event.