Is it necessary to use "laysh" and "3andi" together? Cant just one of them be used if they mean exactly the same?
No, they are not the same.
Laysa = Not
3ind + i = at + me
So as a whole: Not/at-me (I do not have)
Where can I find "I have, you have" etc in writing big enough to read? Why doesn't Duo give us this before we get the exercises?
Before you start the lesson, look for a lightbulb or a Tips button somewhere in the box with the "start" button. It depends on your device, though. I use my laptop so I can see the tips, my phone doesn't show them.