。
She advanced toward the goal step by step.
Literal
She [topic-は] step-by-step goal [toward-へ] advance-went.
一歩一歩 ('step by step') is reduplicative — the noun 一歩 ('one step') is repeated to convey gradual, methodical progression. This kind of noun reduplication is productive in Japanese for emphasis or distribution: 一つ一つ ('one by one'), 日一日 ('day by day'), 年々 ('year after year'). 進んで行く is a compound verb stack: 進む ('advance') + 行く ('go') with the connecting て-form, expressing continuing forward motion away from the speaker's vantage. ゴール is an English loanword that has fully naturalized — used in sports (sports goals), board games, and metaphorical objectives.