Making an app in 3h and getting the first sale (jeannen.com)

Looks neat and you have good drive. There are a few spelling mistakes that would turn me off from using the service are you using a spell check?

Mail.ru (the Russian web portal / email service) does photo colorization and restoration very effectively (and for free) in their 9 May project. It's intended for old damaged military photos but I've had good results with various other ones.

Engineering write-up: https://habr.com/ru/company/vk/blog/459696/

Actual Site: https://9may.mail.ru/restoration/?lang=en

So by app you actually mean webapp? For some reason I thought you meant you created an ios/android app, but I couldn't find any references to this.