In most cases the Free lets Encrypt SSL is fine, but should you need to uninstall it follow these steps:
1. Login to your hosting control panel and find "Hosting Settings"
2. In the Security section select another option besides the Let's Encrypt certificate. "Not selected" for example and hit "Apply".
3. navigate back to your main website and domains page, and click SSL/TLS Certificates.
4. Select your Let's Encrypt certificate and click "Remove".