flutter developer for an app

looking for an flutter developer to develop an app details are: I will need the application which will have: 1) central diary for the driving school visible to me, 2) seperate diaries for instructors where they can manage , set up by themself. 3) There needs to be function of collecting details of the customer which can be exported externally as CSV file. 4) Option of Confirmation of Terms and Conditions of the School by signature. It is not possible to access an app if customer doesn't confirm Terms and Conditions. 5) I can sent via sms application download invitation to customers 6) Central App will send to customers a reminder about lesson 24 hours before. 7) Private chat with customer through the app chat 8 Different lessons with changable pricing 9 GDPR info Maybe there will be some other simple functions. I would like to find out how long will it take to create such a app. i am sure there are some templates which can be customised. As well i would like to find out of you offer Customer Support after that. As I had very bad expierence before where app was badly coded and was constantly crashing. Answering my questions will help me to assess your offer.