〜てあげる
Do something for someone elsemachine translation
FormationVerb て-form + あげる（やる／さしあげる）
〜てあげる expresses doing something FOR another person as a favor: 妹に本を読んであげました (I read a book to my little sister). The direction of the favor is exactly like あげる: from you (or someone on your side) outward to another person.
Be careful of the self-congratulatory nuance: because 〜てあげる explicitly says "I'm doing you a favor", using it directly with the listener — especially a superior — sounds condescending. Don't say 手伝ってあげます to your teacher; say 手伝いましょうか instead (offering help with 〜ましょうか, as learned at N5). This pattern is safest when recounting how you helped a third party, someone younger, or a close friend.
The form changes with the recipient: 〜てやる (for children, animals) → 〜てあげる (equals) → 〜てさしあげる (superiors — but for exactly the self-congratulatory reason above, this form is also rarely said directly to the person).
Examples
私は妹に本を読んであげました。
I read a book to my little sister.
友達に東京を案内してあげました。
I showed my friend around Tokyo.
おばあさんの荷物を持ってあげました。
I carried an elderly woman's luggage for her.