i want to downgrade my plan, but it shows me this massage "You have multicurrency feature turned on in your QuickBooks Essentials TRIAL. This feature can't be turned off

Thank you for sharing the error message you received, Webalo-Mena. Once the multicurrency feature is turned on in QuickBooks, it cannot be turned off because the system must continuously manage currency conversion data.
 

Additionally, the multicurrency feature is not supported in QuickBooks Simple Start, which is why you're unable to downgrade your plan. However, I agree with @Chrea that if you'd still like to switch to QuickBooks Simple Start, you'll need to sign up for a new QBO account and cancel your current QuickBooks Essential Trial subscription. 
 

Here's how to cancel your subscription if you directly purchased it from Intuit:

1. Go to the Gear icon (Settings).
2. Under the Profile column, select Subscription and Billing.
3. In the QuickBooks section, select Cancel Subscription or Cancel Online. If you're cancelling a trial, select Cancel trial.

For subscriptions purchased through the Apple App Store or Google Play Store, follow the instructions in this article: Cancel a subscription purchased through Apple App Store or Google Play Store.

After cancellation, you will have read-only access to your data for 90 days. In this period, you can access and export your transactions and data to set up your new subscription.
 

To learn more about the multicurrency feature in QuickBooks Online, read this article: Multi-currency FAQ.

If you decide to resubscribe, refer to this article for guidance on how to do so: Resubscribe to or reactivate QuickBooks Online.

Please don't hesitate to hit the Reply button if you need further assistance with your subscription. I'm here to help you further!