bangeseo gongbuhaeyo.

방 means “room.”
The particle -에서 marks the location where an action takes place. So 방에서 literally means “in/at the room.”

-에 usually indicates a static location (where something is or a destination).
-에서 indicates the location of an action. Since 공부해요 (“(I) study”) is an action, you need -에서.

The base verb is 공부하다, which means “to study.”
공부해요 is simply the polite present-tense form of 공부하다.

1. Start with 공부하다.
2. Drop -하다 and replace it with -해요.
   
   • 공부
     • 해요 → 공부해요.
       This is a regular 하다-verb conjugation in the polite present tense.

Without extra context, present-tense verbs in Korean can express either a habitual action (“I study in the room [as a rule]”) or a near-future/ongoing action (“I am studying in the room [right now]”).
To emphasize that it’s happening right now, you could say 방에서 공부하고 있어요 (“I am studying in the room”).

Yes. Korean often omits the subject when it’s clear, but you can add one for clarity:
저는 방에서 공부해요.
Here 저는 (“I,” polite) makes it explicitly “I study in the room.”

Use the formal-plain ending -습니다 instead of -해요:
방에서 공부합니다.

Add the object with -를/을 after the thing you study. For example:
방에서 한국어를 공부해요.
(“I study Korean in the room.”)

Combine 지금 (“now”) with the progressive form:
지금 방에서 공부하고 있어요.