If you are trying to install Elementor or Elementor Pro and get this error message: “Destination folder already exists”, this means that your Plugins folder already contains a folder for Elementor (or Elementor Pro) and this is why you cannot upload it again.
What you should do in this case, is to log in into your FTP and under wp-content/plugins, delete the relevant folder.
After this, you will be able to upload the plugin from scratch in your WP dashboard.