Publish Queue, History and Event Queue too big

On our current production with several sites and may editors editing content, we are currently experience several problems related to publishing, delayed publishing, index updating. We checked the queues and we have something like:

Master DB:
Publish Queue - 32M items
History - 165k items
Event Queue - 7.4k items

Web DB:
Publish Queue - 0 M items
History - 6.9M items
Event Queue - 1M items

These are huge numbers as you can see. Somehow it seems these queues are not being cleared properly. Would you advise to change the the daystokeep or other configuration related to these queues?

<agent type="Sitecore.Tasks.CleanupPublishQueue, Sitecore.Kernel" method="Run" interval="04:00:00">

<!-- Agent to clean up the event queue -->
<agent type="Sitecore.Tasks.CleanupEventQueue, Sitecore.Kernel" method="Run" interval="04:00:00">


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