doLang — Learn German Properly

The first German learning app that teaches you WHY, not just what.

What makes doLang different

Every other app teaches you sentences. We teach you the logic behind them.

• Color-coded grammar cases — Nominative, Accusative, Dative, Genitive always in the same colors
• The WHY behind every rule — Why does ein become einen? We explain it. Every time.
• AI conversation partner — Speaks back, corrects in real-time, gradually adds pressure
• Public speaking confidence ladder — From solo practice → time pressure → background noise → real-world readiness
• Goal-aware curriculum — Job in Germany? Visa? Citizenship? Path adapts to your life
• Spaced repetition — SM-2 algorithm schedules reviews exactly when your brain is about to forget
• Level certificates — A1 through C2, shareable on LinkedIn

Stack

Layer	Tech
Frontend	Next.js 14 (App Router), TypeScript, Tailwind CSS
Backend	NestJS, TypeScript
Database	PostgreSQL + Prisma ORM
AI	Claude API (Anthropic)
Speech-to-text	Deepgram
Text-to-speech	ElevenLabs
Auth	JWT (email/password)
Payments	Stripe
Storage	Cloudflare R2
Infra	Vercel (web) + Railway (api)

Project structure

sprich/
├── apps/
│   ├── web/          Next.js frontend
│   └── api/          NestJS REST API
├── packages/
│   ├── types/        Shared TypeScript types
│   └── db/           Prisma schema + migrations
└── content/
    └── curriculum/   Lesson content JSON (A1–C2)

Getting started

git clone https://github.com/msuhaib-03/sprich.git
cd sprich
npm install

# create apps/api/.env and apps/web/.env.local with your keys
cp apps/web/.env.local.example apps/web/.env.local
# fill in your keys

cd packages/db && npx prisma migrate dev && npx prisma db seed
cd ../.. && npm run dev

Web: http://localhost:3000 API: http://localhost:4000/api/v1

Grammar color system

Color	Case	Role
Blue	Nominative	The subject — who does the action
Orange	Accusative	Direct object — what receives the action
Green	Dative	Indirect object — to/for whom
Purple	Genitive	Possession

Article genders: Blue der (masculine) · Pink die (feminine) · Green das (neuter)