DeutschTutor - AI German Learning Agent

AI-powered German learning app with 10,257 words, 1,392 exercises, FSRS spaced repetition, and conversational AI agent — helping migrants in Switzerland master German from A1 to C2.

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Inspiration

As a Ukrainian migrant in Switzerland, I experienced firsthand how critical German language skills are for integration — finding a job, understanding contracts, navigating daily life. Existing language apps are generic and expensive. I wanted to build something free, specifically designed for migrants, covering A1 to C2 with real-world Swiss German context.

What it does

DeutschMentor is an AI-powered German learning agent with:

  • 10,257 vocabulary words across all CEFR levels (A1–C2) with translations in 10 languages
  • 1,392 grammar exercises — fill-in-the-blank, multiple choice, reorder, translate
  • 120 quizzes with 1,860 questions and 120 dictation exercises
  • AI Conversation Agent — powered by Gemini, practices real German dialogues, corrects mistakes, explains grammar in context
  • FSRS v5 spaced repetition — scientifically optimized flashcard scheduling
  • Placement test — automatically detects user's level at first launch
  • Swiss German mode — teaches local vocabulary and expressions
  • Interview preparation — dedicated phrase category for job interviews (Vorstellungsgespräch)

How I built it

  • Android app: Kotlin + Jetpack Compose + Material 3
  • Database: Room (SQLite) with 15,000+ pre-populated entries
  • AI Agent: Google Cloud Agent Builder + Gemini 2.0 for conversational practice, exercise generation, and adaptive feedback
  • Algorithm: FSRS v5 for optimal spaced repetition scheduling
  • Architecture: MVVM + Clean Architecture with Hilt DI
  • Audio: Android TTS for pronunciation, SpeechRecognizer for speaking practice

Challenges I ran into

  • Building a comprehensive curriculum from A1 to C2 with accurate translations in 10 languages
  • Implementing FSRS v5 algorithm correctly for spaced repetition
  • Making AI conversations feel natural while ensuring grammatical corrections are educational
  • Balancing free access for refugees with sustainable monetization

Accomplishments that I'm proud of

  • 10,257 words and 1,392 exercises — one of the most comprehensive free German learning apps
  • Special promo code (HELPFORUKRAINE26) giving Ukrainian refugees free Premium access for 1 year
  • 336 unit tests ensuring quality
  • 10 interface languages making it accessible to diverse migrant communities
  • Published on Google Play Store

What I learned

  • How to integrate Gemini API for educational AI agents
  • Advanced spaced repetition algorithms (FSRS v5)
  • Building accessible, multilingual Android apps at scale
  • The importance of cultural context in language learning

What's next for DeutschMentor

  • Deeper Google Cloud Agent Builder integration for personalized learning paths
  • iOS version
  • Community features — learners helping each other
  • More Swiss German content and dialect recognition
  • Integration with Swiss integration programs (HEKS, Caritas)

Built With

  • android-tts
  • fsrs-v5
  • gemini-2.0
  • google
  • google-cloud-agent-builder
  • hilt
  • jetpack-compose
  • kotlin
  • ktor
  • material-3
  • play
  • room-sqlite
  • speechrecognizer
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