How to Insert Transaction and Update Member on button click.

global class InsertTransaction {

WebService static string  InsertRecord(string id) {

    String OppId=id;
    string ErrorMesg;
    Map<ID,Member__c> mapmembers = new Map<ID,Member__c>();
    List<ID> MemberIDs =new List<ID>();
    List<ID> ProgramEnrIds =new List<ID>();
    List<Transaction__c> listTrans=new List<Transaction__c>();
    List<Member__c> lopp1=[select id ,Active__c,Program_Enrolled__c,Enrolled_Date__c,
    Loyalty_Enrolled__c,Points__c from Member__c where id =:OppId limit 1];
    integer counIn=[select count() from Transaction__c where Member__c =:OppId ];
    set<string> setPromId = new set<string>();
    List<Member__c> Members =new List<Member__c>();
    if(counIn > 0) {
    ErrorMesg ='You can not create a Transaction because this member having the Transaction ';
    }

    else {
    for(Member__c m:lopp1){
    Transaction__c tObj=new Transaction__c(Transaction_Date__c=system.today());
    tObj.Member__c=m.id;
    tObj.ProgramEnrolled__c=m.Program_Enrolled__c;
    tObj.Sub_Type__c='Enrollment';
    tObj.Status__c ='Processed';
    tObj.Loyalty_Product__c='a0590000008at2y';
    listTrans.add(tObj);
    }
 
    for(Transaction__c tObj1:listTrans){
    ProgramEnrIds.add(tObj1.ProgramEnrolled__c);
    MemberIDs.add(tObj1.Member__c);
 
    }
 
 list<Promotion__c > lisProm=[select id,Active__c,Program_Enrolled__c,Apply_To__c from                  Promotion__c where Program_Enrolled__c In : ProgramEnrIds];
    System.debug('lisProm---->'+lisProm.size());
    for(Promotion__c obj:lisProm){
    setPromId.add(obj.id);

    }
    list<Rule_Action__c>ListObj=[Select PointsAssigned__c,        id,Number_of_Points__c,Promotion__c,Promotion__r.Apply_To__c,
 Object__c from Rule_Action__c where Promotion__c in:setPromId];
    System.debug('ListObj---->'+ListObj.size());
 
    Members =[Select Points__c FROM Member__c Where ID in:MemberIDs];
    System.debug('Members ---->+Members )');
 
    for(Member__c m:Members){
    mapmembers.put(m.id,m);
    System.debug('mapmembers---->'+mapmembers.size() );
    }
 
    for(Transaction__c tn:listTrans){
    Member__c Member = mapmembers.get(tn.Member__c);
    System.debug('Member ---->'+Member);
 
    for(Rule_Action__c raObj:ListObj){
    if(raObj.Promotion__r.Apply_To__c == 'Enrollment'){
    Member.Points__c=raObj.Number_of_Points__c;
    System.debug('Member Points---->'+Member.Points__c );
    System.debug('raObj Points---->'+raObj.Number_of_Points__c);
    }
     mapmembers.put(Member.id,Member);
    }
    }
 
    if(listTrans.size()>0){
    Insert listTrans;
    System.debug('mapmembers---->'+mapmembers.size());
    }
 
    update mapmembers.values();
 
    ErrorMesg='Transction created succesfully';
 
    }
      return ErrorMesg;
   }

 }