This is PageFly - Free Landing Page Builder. I would love to provide my recommendations for your store based on 6 years of providing solutions for about 100.000 active Shopify merchants.
Regards your concern to alert when product is low stock or out of stock, i have found this on Shopify app store: https://apps.shopify.com/sold-stock
Hope this can meet your requirements
If you feel my answer is helpful, like it or mark it as a solution. Let me know if you have any questions.
Best regards,
PageFly