We have a managed package that connects our Salesforce org to an external application. Some fields from the managed package are writing information from Salesforce to the external app. So I want to write a trigger that modifies those fields. But I can't install the managed package in my sandbox and I can't create the fields in my sandbox since they have a namespace prefix. So any code I write just keeps throwing an error and not letting me save.
Is there any solution to this when you can't install the managed package in a sandbox?