What is a one-sentence summary of the following article?
You'll find it in the app drawer. Use this method to cancel your paid subscription to Dropbox Plus or Professional if you are billed through the Play store/Google. This downgrades your account to the Basic level without deleting your entire account or the files inside. If canceling puts your Basic account over the storage quota, your automatic syncs will be paused until you delete excess files manually. It's at the top-left corner. A list of all subscriptions you have through Google Play will appear. This displays details about your subscription.  A confirmation message will appear. Once you've confirmed, your subscription will remain active until the final date of the current billing cycle. At that point, your account will be downgraded to Dropbox Basic, the free version of Dropbox. If you want to delete your entire Dropbox account, see the Deleting Your Account method.

Summary:
Open the Google Play Store  on your phone or tablet. Tap the ☰ menu. Tap Subscriptions on the menu. Tap Dropbox. Tap Cancel subscription. Select a cancellation reason and tap Continue. Tap Cancel subscription or Cancel trial.