grammar - Can が be interchanged with を？

I've got a sentence which, I believe, has to be translated in Japanese using "Aの方がC" construction.

Anna learns Japanese more (than for example English)

Can I translate it as 「アンナは日本語の方をたくさん勉強します」?

Or is it possible to write it this way: 「アンナは日本語の方がたくさんを勉強します」？

UPD: I might've misinterpreted the sentence due to wrong emphasis, since the original sentence is in Russian.

Anna learns Japanese more (than somebody else)

So, basically, it is 「アンナの方が日本語をたくさん勉強します」

But what if the emphasis was on Japanese?

Answer

アンナは日本語の方をたくさん勉強します。

This sentence is fine.

xアンナは日本語の方がたくさんを勉強します。

This sentence has two problems.

1. You have 日本語の方 as the subject (marked by が) of 勉強する, but it is not the Japanese that is doing the studying; it is Anna.


2. You have たくさん as the object (marked by を) of 勉強する, but Anna is studying Japanese. She is not studying たくさん.

アンナの方が日本語をたくさん勉強します。

This sentence is fine.

You ask "But what if the emphasis was on Japanese?". I think you answered that with your first translation, didn't you?