。
My friends celebrated my success.
Literal
Friends [subject-が] my success [object-を] celebrated [for me-くれた].
祝う ('to celebrate, congratulate') + the inward benefactive ~てくれた marks the celebration as a kindness done for the speaker. 成功 ('success') is a kango compound — 成 (achievement) + 功 (merit). The が here presents the celebration as a piece of news rather than a comment on a known topic.