Why is my split screen option greyed out on MacBook Air?

I am new to Apple, have just bought a MacBook Air M2. I am used to using two screens for uni, 1 with my word doc and one with all my research webpages. I was told after I bought this Macbook, that I cannot use 2 screens (disappointing). If that is not possible, I need to have a word doc open with my research webpages on the same screen. I hovered over the green dot but the options are greyed out to split the screen. 5 minutes later, it is now not greyed out and I can split screen into 2 webpages but when I open a word doc, my webpage goes and a message saying 'no windows available' comes up. Please help, uni is back in 3 days.

[Re-Titled by Moderator]