First, I’m not a developer and this is my first time attempting to create a Visualforce page and, I’m sure this is very basic to most on here, but I need some help. What I want to do: Override the “New” button on a custom child object to Contacts. The object is called Equipment Assignments and I want users to be able to request equipment from their Contact record in Salesforce. So I want to call the button “New Equipment Request.”  Basically, I want the user to create the record, the have it go through an approval process so the project manager can approve or disapprove the request.
 
I have created the VF page with the below code and when I preview it, everything looks right. I’ve created my custom button and placed it on the related list, shown in the image. However, when I click on the New Equipment Request button, I get the error “Id value 0033C000006pAjR is not valid for the Equipment_Assignments__c standard controller”. So, obviously I need to do more, but I don’t know what that is. I’ve read some posts about public class and wrapper class, but I’m not sure how to go about writing any of that or what exactly I would even need.

Also, I am using record types on the Equipment Assignments, so I need to incorporate that into the VF. I also want to pull in some custom information from the contact record, such as the Manager and Department. I’m not sure how to do that.
 
<apex:page standardController ="Equipment_Assignments__c">
<apex:form >
   
<apex:pageBlock title="Equipment Request">
   
  <apex:pageBlockSection title="Requestor Information">
    <apex:inputField value="{!Equipment_Assignments__c.name}"/>
  
    <apex:inputField value="{!Equipment_Assignments__c.Department__c}"/>
    <apex:inputField value="{!Equipment_Assignments__c.Assigned_To__c}"/>
    <apex:inputField value="{!Equipment_Assignments__c.Project__c}"/>
       
    </apex:pageBlockSection>  
  <apex:pageBlockSection title="Request Information">
    <apex:inputField value="{!Equipment_Assignments__c.Start_Date__c}"/>
    <apex:inputField value="{!Equipment_Assignments__c.End_Date__c}"/> 
 
      <apex:commandButton value="Submit Request" action="{!save}"/>
   </apex:pageBlockSection>
   
</apex:pageBlock>   
</apex:form>
</apex:page>