Log in on a website and get data

So i am trying to make a mobile app for our school online system.

Its a website where you need to log in and then it shows you what marks you have and stuff. I want to be able to fill in a form in the mobile app, then send the data from the form to the website. It will log in to the website and then get the data from the website and display it in the UI.

I hope you get it :D

This is the website: https://izds.skolahostivar.cz/prihlaseni/prihlasit/