Delay when loading records in datatable

I have a table with 3,000 records, when loading the page it takes too long. I have another table with 16,000 records and it's worse because if it takes too long, it goes wrong.

You can help me solve that problem. I read out there that it can be solved with server side but it does not work for me and the error message comes out.

Also this example and the same:

$(document).ready(function() {
$('#example').DataTable( {
"processing": true,
"serverSide": true,
"ajax": "../server_side/scripts/server_processing.php"
} );
} );

Thanks for your help