Code is not flexible. Quality is low.
1. Need to recode voice speaking totally. Now it's a static parameter for EN only, other langs sounds scary.
2. Yandex Translator is free up to 1m words/month. Than it will be not free, but $15 at least.
3. When you try to reskin the app, you will understand that you need to recode the layout completely. A lot of extra work.
And the rest is a very good application, buy it if you have a developer who can help you to release it. Without programming knowledge you cannot do this.