notadictionary.com
オレが大好きだったギタリストがバンドを辞める時理由を聞いたら…
→ “When I asked why the guitarist I loved so much was quitting the band...”
オレ ore = I (casual masculine pronoun)
が ga = subject marker particle
大好き daisuki = love dearly / love very much (adjective phrase)
大 dai = big / large
好き suki = like / love
だった datta = was (past tense of 'to be' for nouns)
ギタリスト gitarisuto = guitarist (loanword)
が ga = subject marker particle
バンド bando = band (loanword)
を o = object marker particle
辞める yameru = to quit / to resign (verb)
時 toki = time / when (noun)
理由 riyuu = reason (noun)
を o = object marker particle
聞いたら kiitara = if/when I heard (conditional form of 'to hear')