What to use when creating an application for a university?

Question

Mobile development

In connection with distance learning in all universities and schools (and I myself am a student, to be more precise, the head of the group and stream), the idea of ​​​​creating a small application with functionality similar to the Electronic Educational Environment for fellow students came up. (now every university has such a thing).

spoiler

Опыта в программировании практически не имею, однако общие принципы понимаю, сайты создавал, с БД работал.

So, what is needed from the application:

1. Storage of educational materials - lectures, abstracts, literature. It is necessary that the student himself can upload his notes or work to the application or upload the textbook he needs to his device. The first question follows from this: Do I need to use some kind of cloud (Google Drive?) Or is it better to use some kind of paid hosting?
   
2. Alert system - the headman wrote a message and chose from the list of students to whom to send it. The message came to everyone as a notification on the phone. It turns out you need some kind of notification server?
   
3. Class attendance table. Embed Excel somehow in the application?
   
4. The app needs to be made for both iOS and Android. Is it better to make it native? Then choose better Java or Kotlin for Android? I am familiar with Swift for iOS. Or is it better to do not native? Whereas? I know that the question is too stupid and global, but the attempt is not torture :)
   

You can answer all questions as briefly as possible, at least just name the technology you need to use, just point me in the right direction.

ps

Понимаю, что все вопросы звучат глупо, что использую не те термины и так далее, просто хочу не тратить время зря на карантине и всем этим заняться (энтузиазма много). Всем заранее спасибо и удачи!