Any advice is welcome.

Hello and thanks for advice in advance.     I am new to this.   I am trying to export video from premier rush on my iPhone XS Max.  It keeps saying storage is almost full.   Change cloud storage in settings.   I have a ton of storage free on my iPhone and also cloud.   I am using the free version of the rush because the App Store doesn't give an option to buy it or subscribe.   Is the free version causing this, or could it be another issue.   Thank you so much for your time.