How can I share the screen in the Android app?

How can I share the screen in the Android app?
Maybe a stupid question. I’m sorry. I am a teacher and try to teach online in Corona times.
I use the app on my Samsung S4 Android tablet. Unlike on the browser, there is no button at the bottom left to share the screen.
That would be very important. The tablet has a pen. I would like to write something and explain mathematics to the students.
So they only see my face. Math would be more important now.
Thanks a lot

Hello @damencho any option to enable screen shareing on mobile phone may be via browser or via app.