"I go if he goes."
Translation:אני הולך אם הוא הולך.
That's ok too. I'd say, usually אני הולך אם הוא הולך would mean "only if he goes". אם הוא הולך אני הולך means if he goes I definitely go. But context and intonation can switch that around.
This question could be considered a little confusing. It could also be acceptable to write אלך אם ילך, in the future tense.