以前こちらで働いていたことがあります

N3 以前 izen before, previously, in the past N5 こちら kochira this way, this side, this person, polite N5 ことがあります koto ga arimasu have done before / sometimes happens

N4 以 i / motsu.te by means of, because, in view of N5 前 zen / mae, -mae in front, before, devant N3 働 dou / hatara.ku work, (kokuji), travailler

N3 〜ことがある koto ga aru Indicates past experience or occasional occurrence, attaches to a verb, means have done before or sometimes happens N5 〜ている te iru Indicates ongoing action, continuous state, repeated habit, or resulting condition depending on context N5 〜ます masu Used at the end of verbs, polite present or future form, makes the sentence more polite N5 〜が ga Marks the grammatical subject, highlights new information, can also show slight contrast in some sentences N5 〜で de Indicates where an action happens, means used, tool, cause, or material depending on context N5 〜と to Indicates company, quotation, natural condition, complete list, or direct connection between elements