Hi , 

I need help in the below code and I am thankful to any suggestion you give in here to correct the code
I have a requirement to create a visualforce page which takes the contactId from the URL and create new Emergency Contact Information__c(custom object ) related record  to the contact record.  The contact and  Emergency Contact Information__c are in master detail relationship.

public with sharing class ChildContactControllerApex {
    public Contact mycontact {get; set;}
    private List<Emergency_Contact_Information__c> listToInsert= new List<Emergency_Contact_Information__c>();
         public ChildContactControllerApex(ApexPages.StandardController controller) {
    }
     
    public pagereference save()
    {
          String ContactId = ApexPages.CurrentPage().getparameters().get('Id');
           List<Contact> cnt = New List<Contact>([SELECT Id, Name ,(Select Name , Emergency_Contact_Relationship__c, Emergency_Contact_Phone__c from Emergency_Contact_Informations__r)
                                  from Contact WHERE Id = :ContactId ]);
        if(!cnt.isEmpty())
        {
          if(cnt[0].Emergency_Contact_Informations__r.size()>0){
             cnt[0].Emergency_Contact_Informations__r[0].Contact__c= contactId;
              cnt[0].Emergency_Contact_Informations__r[0].Emergency_Contact_Relationship__c=mycontact.Emergency_Contact_Relationship__c;
              cnt[0].Emergency_Contact_Informations__r[0].Emergency_Contact_Phone__c=mycontact.Emergency_Contact_Phone__c;
               update cnt;
            }
           else
           {
            Emergency_Contact_Information__c EmergencyContact = new Emergency_Contact_Information__c();
            EmergencyContact.Contact__c= mycontact.Id;
            EmergencyContact.Emergency_Contact_Relationship__c= mycontact.Emergency_Contact_Relationship__c;
            EmergencyContact.Emergency_Contact_Phone__c =  mycontact.Emergency_Contact_Phone__c;
              listToInsert.add(EmergencyContact);
            }
            if(listToInsert.size()>0){
            Insert listToInsert;
            }
          }
            return null;
    }}
    
Visualforce page 


<apex:page standardController = "Contact" extensions= "ChildContactControllerApex"> 
<apex:form >
<apex:pageBlock title="Please Update Emergency Contact Information" mode="edit">>
<apex:pageBlockSection >
     <apex:outputField value="{!myContact.FirstName}"/><br></br>
     <apex:outputField value="{!myContact.LastName}"/><br></br>
     <apex:inputField value="{!mycontact.Emergency_Contact_Informations__r.Name}"/><br></br>
     <apex:inputField value="{!mycontact.Emergency_Contact_Informations__r.Emergency_Contact_Relationship__c}"/><br></br>
     <apex:inputField value="{!mycontact.Emergency_Contact_Informations__r.Emergency_Contact_Phone__c}"/><br></br> 

</apex:pageBlockSection >

<apex:pageblockbuttons >
     <apex:commandButton value="Save" Action="{!Save}"/>
</apex:pageblockbuttons>

</apex:pageBlock>
</apex:form>
</apex:page>