As a parent with hearing impaired kids, I can’t stress enough how bad of an idea this product is. If you think you need this device you should get properly tested and if needed, fitted with a properly programmed hearing aid.
The Washington Post disagrees with you: https://www.washingtonpost.com/national/health-science/have-hearing-problems-cheaper-nonprescription-devices-might-help/2015/12/09/afd752fa-84bf-11e5-a7ca-6ab6ec20f839_story.html
Depends on the type of hearing loss. If you have poor hearing across all frequencies, then yes. But if you have selective frequencies that you can’t hear, amplifying ones that you don’t have issues hearing can cause more damage. Ask any audiologist.