How to update the plugin?
Updating through FTP
Simply overwrite the plugin files with the new version files via FTP, then deactivate and activate back the plugin.
Updating via the WordPress Installer
Set the ‘Keep Settings’ to ON in the General Settings tab under the Settings / Contact Form Slider. Deactivate and delete the plugin, then install the new version as a new plugin (Add New). With turning on the ‘Keep Settings’ option, the plugin will keep the configuration datas, so you don’t have to set it up again.