Learn Hardcore Japanese: gakusei ha nihongo to eigo wo benkyousimasu.

In Japanese, you often omit pronouns when context makes them clear. Here 学生は (“as for the student”) is the topic, so you don’t need 私は (“I”) or 彼は (“he”). It’s understood that the student is doing the studying.

What does the particle は after 学生 mean? Why not use が?

は marks the topic of the sentence—the thing you’re talking about. It sets 学生 (“student”) as the theme. が marks the subject when introducing new info or emphasizing it. Since 学生 is already the known topic, は is the natural choice.

What role does the particle と play between 日本語 and 英語?

Here, と functions as “and,” connecting 日本語 (“Japanese”) and 英語 (“English”) in an exhaustive list (both languages are studied). If you wanted a non-exhaustive list (e.g. “…and other things”), you’d use や instead.

Why is there only one を after 英語 instead of one after each language?

When you link nouns with と, you can attach the object marker を to the final noun only. The single を then applies to the whole phrase 日本語と英語, marking both as the verb’s direct objects.

What kind of word is 勉強します? Is 勉強 a verb?

勉強 is a noun meaning “study.” When combined with する (to do), it becomes a suru-verb: 勉強する (“to study”). In polite form, する becomes します, so 勉強します = “study(s).”

How do I make this sentence past tense (“studied”)?

Change 勉強します to its past tense 勉強しました. The sentence becomes:
学生は日本語と英語を勉強しました。

How can I express “I’m studying Japanese and English” if I’m talking about myself?

Use the progressive form 勉強しています to show an ongoing action. For example:
（私）は日本語と英語を勉強しています。
You can omit 私 because it’s clear from context.

What if I want to list three languages, like Japanese, English, and Chinese?

If you want an exhaustive list use と between each:
学生は日本語と英語と中国語を勉強します。
If you want to imply “among others,” use や:
学生は日本語や英語や中国語を勉強します。