[FREE] MMT - Tutoring Mathematics

I would like to introduce my second App MMT. MMT is basicly a pocket calculator that executes the calculation step by step, and each step is explained using the text to speech engine.
Currently I can support columnar addition and subtraction using the american method. Division, multiplicationand perhaps subtraction using the Austrian method are planed.
The explanation is available in English and German. I think about French or spanish, but at the moment I don’t even know how kids learn basic arithmetic operations there. Any input on how to localice such an app would be appreciated. I would also like to hear some in general feedback.
MMT is available on Google Play with this URL https://play.google.com/store/apps/details?id=de.thomaslankes.mmt
Best regards,