Hi, I am still in the early days of my apex journey so trying to get my head around basic concepts.

I have built a simple enough trigger which does the following. When somebody is creating or update a lead it looks at the values in 6 key fields and then counts the number that are not null. It then enters that value in the 'Key fields' field on the lead record.

Secondly if this value is greater than or equal to three it creates a task for each of the completed key fields.

So far I have gotten the first stage of the process to work by using before insert and before update. However now since the task record will require a lead ID I suspect I will need to use 'after update/insert' capabilities.

What would you suggest is the best way to modify my code to account for these two requirments.
 

trigger KeyFieldsPopulated on Lead (before insert, before update) {
     
    for (Lead l : Trigger.New) {
        //Create list to store key fields 
        List<String> KeyFields = new List<String>();
        KeyFields.add(l.FirstName);
        KeyFields.add(l.LastName);
        KeyFields.add(l.Email);
        KeyFields.add(l.Phone);
        KeyFields.add(l.Website);
        KeyFields.add(l.Title);
        
        
        //Create list to store key fields that have a value
        List<String> KeyFieldsPopulated = new List<String>();
        
        //Create a counter variable to track how many key fields have a value
        Integer counter = 0;
        
        //Loop through the key fields 
        for (Integer i = 0; i<KeyFields.size(); i++) {
            if (KeyFields[i]!=null) {
                KeyFieldsPopulated.add(KeyFields[i]);
                counter = counter + 1;
                
            }
            l.Key_Fields__c = counter;
        }
        
            //Loop through the populated key fields and create a task
            if (counter >= 3) {
                for (Integer j = 0; j < KeyFieldsPopulated.size(); j++) {
                    Task t = new Task();
                    t.Subject = 'Verify the '+ KeyFieldsPopulated[j] + ' field';
                    t.WhatId = l.Id;
                }
             
          }
       
    }

}