Standard page layout line break

Question

I'm not sure if this is even possible in a standard page layout, I have Long Text Area(32768) on a custom field Message__c so the data I have is with line break as shown below and I have tried \n but I'm getting everything in one line.

I'm trying to achieve something like this:

This is a line one 
this is a line two 
this is a line three 
Last line

Answer 1

Not sure I have understood your question correctly.

I am updating Case Description field (which is LongTextArea(32000)) from Developer console like this:

Case obj = [SELECT Description FROM Case WHERE Id = '500q0000006XBEP'];
obj.Description = 'First Line' + '\n\r' + 'Second Line' + '\n\r' + 'Third Line';
update obj;

And it is showing in UI:

If I print that in debug log:

Case obj = [SELECT Description FROM Case WHERE Id = '500q0000006XBEP'];
System.debug('description=' + obj.Description);

It gives me:

Update based on comments:

If you just press ENTER button to put in new line like this:

That will give me results:

2nd Update from Comments:

if you are receiving text like this

This is a line one <br> this is a line two <br> this is a line three <br>Last line

Then just replace <br> with \n\r before assigning that into the field and it will work.

Case obj = [SELECT Description FROM Case WHERE Id = '500q0000006XBEP'];
String str = 'This is a line one <br> this is a line two <br> this is a line three <br>Last line';
obj.Description = str.replace('<br>','\n\r');
update obj;