Are you free for a lesson next Saturday at two o'clock?
Are you available for a lesson at 2:00 p.m. next Saturday?
ーAre you free for a lesson next Saturday at two o'clock in the afternoon?
「来週の土曜の午後2時にレッスンは空いていますか?」
Are you free for a lesson? で「レッスンは空いていますか?」
next Saturday at two o'clock in the afternoon で「来週の土曜の午後2時」
available を使っても言えますよ。
ーAre you available for a lesson at 2:00 p.m. next Saturday?
「来週土曜の午後2時にレッスンは空いていますか?」
Are you available for a lesson? で「レッスンは空いていますか?」
at 2:00 p.m. next Saturday で「来週の土曜の午後2時」
ご参考まで!