i have written the below trigger
trigger CountVistorOnCustomer on Visit__c (After insert) {
     Id devRecordTypeId = Schema.SObjectType.Visit__c.getRecordTypeInfosByName().get('Existing Customer Visit').getRecordTypeId();
    
    List<Account> ct = new List<Account>();
    List<Account> ct1 = new List<Account>();
    List<Account> ct2 = new List<Account>();
    List<Account> ct3 = new List<Account>();
    set<Id> customerId = new set<Id>();
    Integer orgFiscalMonth = [SELECT FiscalYearStartMonth FROM Organization].FiscalYearStartMonth; //april
    Date orgFiscalYearStart = Date.newinstance(system.today().year(), orgFiscalMonth, 1);//2020-04-01
    Date orgFiscalYearEnd = Date.newinstance(system.today().year(), orgFiscalMonth + 11, 31);
    
    Integer PreviousYear = system.today().year() - 1;
    Integer NextYear = system.today().year() + 1;
    Integer CurrentYear = system.today().year();
    
    if(Trigger.isInsert) {
        for(Visit__c v1:Trigger.New) {
            customerId.add(v1.Customer__c);   
            
        }   
        
    }
    
    
    AggregateResult[] groupedResults = [SELECT COUNT(Id), Customer__c FROM Visit__c
                                        where Customer__c IN :customerId and 
                                        VisitDate__c>=:orgFiscalYearStart 
                                        and VisitDate__c<=:orgFiscalYearEnd
                                        and RecordTypeId ='012O0000000KkAVIA0'
                                        GROUP BY Customer__c  ];
    AggregateResult[] groupedResults1 = [SELECT COUNT(Id), Customer__c FROM Visit__c
                                         where Customer__c IN :customerId 
                                         and VisitDate__c = LAST_FISCAL_QUARTER
                                         and RecordTypeId ='012O0000000KkAVIA0'
                                         GROUP BY Customer__c  ];
    AggregateResult[] groupedResults2 = [SELECT COUNT(Id), Customer__c FROM Visit__c
                                         where Customer__c IN :customerId 
                                         and VisitDate__c = THIS_QUARTER
                                         and RecordTypeId ='012O0000000KkAVIA0'
                                         GROUP BY Customer__c  ];
    
    for(AggregateResult ar:groupedResults) {
        
        Id custid = (ID)ar.get('Customer__c');
        Integer count = (INTEGER)ar.get('expr0');
        Account cust1 = new Account(Id=custid);
        cust1.Current_FY_for_Report__c = count;
        ct1.add(cust1);
        
    }
    for(AggregateResult ar:groupedResults1) {
        system.debug('Trigger Fired groupedResults second one'+groupedResults1);
        Id custid = (ID)ar.get('Customer__c');
        
        Integer count1 = (INTEGER)ar.get('expr0');
        
        Account cust1 = new Account(Id=custid);
        
        cust1.Previous_Quater_For_Report__c = count1;
        
        ct2.add(cust1);
        
    }
    for(AggregateResult ar:groupedResults2) {
        system.debug('Trigger Fired groupedResults third one'+groupedResults1);
        Id custid = (ID)ar.get('Customer__c');
        
        Integer count2 = (INTEGER)ar.get('expr0');
        
        Account cust1 = new Account(Id=custid);
        
        cust1.Current_Quarter__c = count2;
        
        ct3.add(cust1);
        
    }
    
    
    system.debug('Trigger Fired ct'+ct);
    update ct1;
    update ct2;
    update ct3;
    ct.addAll(ct1);
    ct.addAll(ct2);
    ct.addAll(ct3);

}


batch class for the same
global class CountVisitorBatch implements Database.Batchable<sObject>{

    global Database.QueryLocator start(Database.BatchableContext BC){
        String query = 'Select ID,Previous_Quater_For_Report__c,(Select Id,Customer__c from Visit__r) from Account'; 
        return Database.getQueryLocator(query);
    }
    
    global void execute(Database.BatchableContext info, List<Account> Accounts){
        list<account> updatedList = new list<account>();
        if(Accounts.size() > 0){
            for(account acc : Accounts){
                acc.Previous_Quater_For_Report__c = acc.Visit__r.size();
                
                updatedList.add(acc);
            }
        }
        if(updatedList.size() > 0){
            update updatedList;
        }
        
    }
    
    global void finish(Database.BatchableContext info){
        
    }
}


But getting error
Variable does not exist: Visit__r

Can someone please help me with the batch class