[SalesForce] How to Query 2 Objects Down Parent to Child SOQL in APEX Class

I'm creating a visualforce related list on the Opportunity record layout. This related list is supposed to show a list of services (object name: QService__c) on the synced quote related to that opportunity.

Here is the class:

public class serviceViewController {

public final Opportunity opp;

public List<Quote> getQServices{get; set;}
public serviceViewController(ApexPages.StandardController controller) {
    this.opp = (Opportunity)controller.getRecord();
    getQServices = [SELECT Id, Name, IsSyncing,
                    (SELECT Id, Name FROM QService__r)
                    FROM Quote
                    WHERE Opportunity__c = :opp.Id AND IsSyncing = true 
                    ];

}}

I'm using a class extension to pull in the filtered data since I need to use a standard controller if I'm going to have this on an opportunity layout.

My thoughts were to originally pull from the quote, and do a downward transversal to the child object (QService__c) of the parent object (Quote). And then on the WHERE statement, pull these fields of the synced quote on the opp. And then display the QService__c fields Id and Name.

I thought this would work because it's referencing the Opportunity and it's going down 1 level from the Quote to the service object (QService__c) but I'm getting this error from the developer console:

    (SELECT Id, Name FROM QService__c)
                          ^

ERROR at Row:2:Column:47
Didn't understand relationship 'QService__c' in FROM part of query call. If you are attempting to use a custom relationship, be sure to append the '__r' after the custom relationship name. Please reference your WSDL or the describe call for the appropriate names.

I don't understand because from what I've been scouring all over online, I'm using the correct reference __r for Parent to Child relationships.

Any help or suggestions on this on why my query isn't working? or if you think I could be doing this in a better way?

And for reference and testing, here is my visualforce code.

<apex:page standardController="Opportunity" extensions="serviceViewController" lightningStyleSheets="true">
<apex:form >
    <apex:pageBlock title="QServices">
        <apex:pageBlockTable value="{!getQServices}" var="qservice">
            <apex:column headerValue="Id" value="{!qservice.Id}"/>
            <apex:column headerValue="Name" value="{!qservice.Name}"/>
            <apex:column headerValue="Is Synced" value="{!qservice.IsSyncing}"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:form>