Overriding an Existing Observer and Event

Sometimes we may not be able to call an event in an external module. So this happens due to some event or observer may be functioning for default function.
in order to override these observers or events we need to create an external module with a di.xml file

here we can give preference to the observer or event

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="--location for existing module--" type="Vendor\modulenanem\--\--" />
</config>