I was planning on watching a play today, but just from looking at the program, I had no idea what it was about.
今日 today
演劇 play/drama/theater
観る watch
予定だ I was planning on ~
演目 program
だけ just
内容が全く分からない no idea what it was about
動詞+予定だという表現は I was planning on +動詞で言えます。
例文 I was planning on watching the baseball today.
「今日は野球を見る予定だ。」
例文 Are you planning on doing anything in the holidays?
「休暇に何かをする予定ですか?」
参考になれば幸いです。