Create an App for Android and iOS

I'm planning a community app. Users should be able to register in this app (email + password, Google, Facebook, etc.). In addition, the user should be able to create a small profile, e.g. with photo, location, nickname. Registration via email + password must be confirmed via double opt-in. The app should be able to access the device's contact lists. Now the user can create a new thread. In this he enters the following information: - Message part 1 (public) - Message part 2 (not public) - Recipient - Date The recipient (from the existing contacts, or an individual entry, e.g. telephone number or email) then receives a message via internal private messaging (if the recipient is also logged in to the app), SMS or, if known, via email. If the notification is sent via email, it will be as follows: --- START OF THE MAIL --- You have received a new message from XY, you cannot open the second part of the message until {date}. {personal message part 1 from XY} [BUTTON TO MESSAGE] [LINK TO MESSAGE] (here the recipient is redirected to a page with further information about the message part1 and part2 and the sender) - I would like to be informed again on {date} [BUTTON to a reminder form] - I would like to register and be notified about the app [BUTTON to a landing page] - I am already registered and would like to be informed about the app [BUTTON to a landing page] You will not be contacted further about this message. User XY or another user of our platform may contact you via our APP. If you generally do not want this, we ask you to let us know here. [LINK to unsubscribe] --- END OF MAIL --- The SMS would look like this: --- START OF SMS --- You have received a new message from XY, you cannot open the second part of the message until {date}. {personal message part 1 from XY} {URL for more information} --- END OF SMS --- ***) All content/programming of the link and button targets are not part of the work When the recipient confirms receipt, the sender should receive a push notification and be able to see this in the list of threads they created. The user should receive an overview of all threads, he can neither change the message nor the date, but only see what data he has saved OR delete the thread. If the recipient has saved a reminder, they will be informed that the thread has been deleted! If the recipient does not respond to the creation message, then the recipient will not receive any further information. Finish.