This is the 2174th most frequent Japanese word.
楽しま
"楽しま" is a conjugated form of the verb "楽しむ," meaning "to enjoy."
In this sentence, 楽しました (tanoshimashita) is used as the past polite form of the verb 楽しむ (tanoshimu), which means 'to enjoy.' It indicates the act of having enjoyed an activity in the past.
友達と映画を思い切り楽しました。
I thoroughly enjoyed the movie with my friends.
Here, 楽しみ (tanoshimi) is used as a noun indicating 'anticipation' or 'looking forward to,' formed from the verb 楽しむ (tanoshimu).
人々は祭りを毎年楽しみにしています。
People look forward to the festival every year.
楽しもう (tanoshimou) is the volitional form of 楽しむ (tanoshimu), indicating a decision or intention to engage in an enjoyable activity.