Personal Assistant App Development

Project Description
I am looking for a developer to build a simple first MVP of a personal assistant app for Android.
The app is initially intended for private personal use only. A UI/design concept already exists and will be provided as image references.
The first MVP should include:
dashboard / home screen based on the provided design
monthly calendar
create, edit and delete appointments
popup showing appointments for a selected day
simple notes
simple projects section
quick access buttons
notification badges on selected buttons
simple reminders / push notifications
a small chat window in the bottom right that opens when tapped
basic ChatGPT / OpenAI API integration
simple natural-language commands, for example:
“Create an appointment for tomorrow at 2 PM”
“Create a note”
“Show me my appointments”
simple news section
ability to define selected news topics of interest
notifications for important news related to those topics
Important:
the existing UI design should be used as a reference
the first version should remain simple and lightweight
clean and understandable code
the app should be structured so it can easily be expanded later
German-speaking developer preferred
Possible future extensions:
email assistant / Gmail / Outlook
automatic email drafts with approval before sending
stock price alerts
dividend dates
scientific research and medical news
more advanced AI assistant features
additional automation and push notifications
optional multi-user support later
Preferred technology:
React Native
Expo
optional Supabase
OpenAI API
Budget / Development Plan
My initial budget is approximately €300 for the first basic MVP.
After the first version, approximately another €200 is available for the next expansion.
If the cooperation works well, I would like to continue developing the app step by step. Smaller future extensions may have a budget of around €50–100, depending on the feature.
I prefer a fixed-price offer for the first phase.
Please tell me:
what can realistically be implemented for the first €300
estimated delivery time for the first version
whether communication in German is possible
how you would structure the app so it can be expanded later