We assure you that our software is absolutely safe and cannot damage your computer. You can verify this by checking the download link on the virustotal.com resource
Probably the SmartScreen blocks the access to the installation file, and you can not download it.
According to the Microsoft Help center, you can temporarily disable SmartScreen in your Internet Explorer, then download Forex Tester and turn it on again. For more information about using SmartScreen Filter please follow the link.