Hello, I work with digital marketing for over 2 years.
I checked your website and trying to download your app however I do not know why it's still loading.
Anyway, first I would suggest you improve the website.
Try affiliate programs, upload your product to websites like clicbank, maxbounty etc and pay affiliates for ex $2 for a download.
Paid ads on Instagram.
Guest posting on blogs.
You either need a really good website, Instagram account (because Facebook will not bring such as good results as Instagram for an app) or just paid ads on social media/google/other apps.
Let me know if you are interested.