Why we need "o" here? ...pe o foaie de hartie. As usual there is no need - pe masa, pe carte etc.
Because the noun "foaie" (sheet) has a determinant of its own "hartie" (paper). In this case either the indefinite or definite article is needed.
"pe o foaie de hârtie"
"pe foaia de hârtie"
Why "foaie de hârtie" and not "foaie hârtii"? Mulțumesc mult.
Because "foaie hârtii" translates as "sheet papers" which makes no sense.
"foaie" = "sheet" | "de" = "of" | "hârtie" = "paper"
I think "Onto a sheet of paper" is probably better English for this example. Thanks.
Paper sheet?