im happy when i see new idea firstly dont think which you said not working ads/ registration all this is way to success but you can use it which who have pronunciation problems and you can make contract with lang.center to give your app as gift to help more faster contact me for any advice
I think you are missing the market research step. You need to ask the people that you would be targeting, because at the moment, I'm unsure why someone would use your product, over say using a platform where they can hire an online tutor and learn from them, or use Rosetta for example. I get that...