You can use automatic update to update the plugin safely.
- Go to Master Slider page on WordPress, download it.
- Remove `/wp-content/plugins/masterslider` directory on your website using FTP
- Extract the downloaded package file and find `masterslider-installable.zip`
- Extract `masterslider-installable.zip` directory to your computer and upload it to `/wp-content/plugins/` directory using an FTP
- Activate the plugin in the Plugins page
If you delete Master Slider in plugins page by clicking on delete button, the uninstall process will be triggered and it will erase all sliders and data related to Master Slider. Please pay attention and always update the plugin by two methods mentioned above .