trigger caseOwnerUpdate on Case (before insert,before update,after update)

if(Trigger.isBefore && Trigger.isUpdate)
{
    System.debug('entered if condition');

    for(Case c : Trigger.new)
    {

        System.debug('Updating logic');
        List<Group> qid = [select Id from Group where Name = : c.Assignment_Group__c and Type = 'Queue'];
          for(Group g : qid)
            {
                c.OwnerId = g.id;
                System.debug('updated');
            }
    }
}

List<Case> updateCS = new List<Case>();
Map<Id,Case> cases = new Map<Id,Case>();

for (Case cs : Trigger.new)
{
    if(Trigger.isUpdate) {
        System.debug('>>>>> Owner ID: '+cs.ownerId+' Temp Owner ID: '+cs.TempOwnerId__c);
        if(cs.TempOwnerId__c <> null && cs.TempOwnerId__c <> '') {
            if(cs.OwnerId <> cs.TempOwnerId__c) {
                cases.put(cs.id,cs);
            }
        }
    }
}
if (cases.isEmpty()) return;

for (Case cs : [SELECT OwnerId,TempOwnerId__c FROM Case WHERE id in :cases.keySet()]) {
    cs.OwnerId = cases.get(cs.Id).TempOwnerId__c;
    cs.TempOwnerId__c = 'SKIP'; //flag to stop infinite loop upon update
    updateCS.add(cs);
}
System.debug('>>>>>Update Cases: '+updateCS);

//
//Update last assignment for Assignment Group in batch
//
if (updateCS.size()>0) {
    try {
        update updateCS;
    } catch (Exception e){

    }
}

}

if(Trigger.isBefore && Trigger.isUpdate)
{
  for(Case c : Trigger.new)
    {
        if(c.Assignment_Group__c=='Tech Support'||c.Assignment_Group__c=='GD-IT'||c.Assignment_Group__c=='App-Support'||c.Assignment_Group__c=='GD-RM'||c.Assignment_Group__c=='GD-DB'||c.Assignment_Group__c=='Dev-Ops'||c.Assignment_Group__c=='App-Management'||c.Assignment_Group__c=='PDT-DS-Engg'||c.Assignment_Group__c=='PDT-US-Engg')
        {
            c.Group_Manager_Email__c = 'sgaware148@gmail.com'; c.Escalation_Level_2_Email__c ='sgaware148@gmail.com'; c.Escalation_Level_3_Email__c='sgaware148@gmail.com';
        }
    }
}