Order by multiple meta keys on wordpress

After multiple research I didn’t find the correct answer to my question.

I need to order my custom post type first by date and then by time.

Here’s what I tried: https://pastebin.com/BRR6h08j

It order well by the date but not by the time. And I need to show everypost (even if the date is passed)

If someone can help me getting my correct meta_keys

I know the problem is here:

'meta_query' => array(
     'relation' => 'AND',
      array(
        'key' => 'heure_de_lartiste',
        'value' => $todaysDate,
        'compare' => '>='
       )
  ),

I don’t know what to put in “value” and “compare”

Thanks a lot,

Jhon