I did't understand a joke

how are you? What about your last weekend?
Today I am writing because I want to tell you what happened the last weekend when I went to a jazz concert. It was an amazing concert, they were four internationals musicians: piano, drums, bass and saxophone. The concert lasted an hour and half, in the middle of the concert, the saxophonist told a joke in English and everybody laughed less except me because I did not understand anything. Then (or: at that moment)  I decided to take classes of conversation ("conversation classes"  is better)  to improve my English. There is a group of five persons and a teacher, they ( we?) meet every afternoon to speak for two hours. If you came to the next weekend I would introduce you to speaking English too.
See you soon
Carmen