Since you have 5 speakers, one of them should be the center speaker, which is focused on dialog. Some Denon receivers have a ‘dialog level adjust’ or ‘center level adjust’ setting that you can turn on and then turn up the dialog level. If you don’t have that setting the solution is to try to turn up the center speaker (or turn down all the other speakers) some way, such as using a mixer or some such (may require some research for specifics).
Since you have 5 speakers, one of them should be the center speaker, which is focused on dialog. Some Denon receivers have a ‘dialog level adjust’ or ‘center level adjust’ setting that you can turn on and then turn up the dialog level. If you don’t have that setting the solution is to try to turn up the center speaker (or turn down all the other speakers) some way, such as using a mixer or some such (may require some research for specifics).