I'm new to Apex in general and cannot seem to get this trigger to work...

I have a custom object LOC that has a related custom object called GPO.

I need to have a trigger that will update a related user field on LOC with the owner of the related GPO.

I need the related user so I can use it in an approval process.

Here is what I have so far and it does nothing. From my research I know maps are needed but I don't understand the concept at this point.

trigger LOCapprover on LOC__c (before insert,before update) {
    for(LOC__c loc: Trigger.new){
        if(loc.LOC_GPO__c != null)
    loc.Receiving_User__c = loc.LOC_GPO__r.Owner.Id;  
        
    }    
}

I have built several Discount formula fields in the Opportunity Product to reflect contract selections from the Account page. The Problem is that i have several fields and i would like to eliminate field that do not need to be shown for that given opportunity.

I heard that I could use Apex Triggers to determine the page layout that is selected.  So my question is two fold, 

1) is that true that i could use a trigger that looks at a field in the Account page to determine the page layout of the Opportunity products for that account.

2) How do i do that? (i'm great with formulas but code not so much i can customize visualforce but i have not written much on my own)

I'm new to Apex in general and cannot seem to get this trigger to work...

I have a custom object LOC that has a related custom object called GPO.

I need to have a trigger that will update a related user field on LOC with the owner of the related GPO.

I need the related user so I can use it in an approval process.

Here is what I have so far and it does nothing. From my research I know maps are needed but I don't understand the concept at this point.

trigger LOCapprover on LOC__c (before insert,before update) {
    for(LOC__c loc: Trigger.new){
        if(loc.LOC_GPO__c != null)
    loc.Receiving_User__c = loc.LOC_GPO__r.Owner.Id;  
        
    }    
}