A free longboard lesson offered by Boardriders cos...

A free longboard lesson offered by Boardriders cost me a broken arm!
My wife and I were planning to learn longboarding so we went to Boardriders store in Barceloneta. Then next to the checkout we saw some flyers saying that they offered free longboard classes every sunday in partnership with a company called Ungravity, which we thought was a great opportunity for us to see how we do as beginners before investing. So we registered using the link on the flyers and in the registration it said it included the boards and helmets as you can see in the screenshot I attached.
We went there on Sunday morning at the planned time. There were about ten people. The instructor gave us boards but no helmets or any kind of protection. He showed us how to stand on the board and skate in front of the store for literally 10 minutes and told us to go skating with him from Barceloneta to Forum which is about 5 kms. We were struggling because it was a Sunday morning and the place was crowded with people walking, running, biking etc. Some people even stopped him to say this wasn't the right place to take beginners. There were many times we couldn't go on and started to walk. So he would come on his skate and pull us while we were trying to stay in balance.
I managed to make it until Poble Nou but unfortunately there was a downhill where the longboard got going faster and I couldn't keep my balance and fell. And apparently I broke my wrist. The instructor bought some ice for me from a market and said that he was going to call me when we left for hospital, but never called. My arm was put in cast and I had to take a sick leave for 55 days. Fortunately I had my own insurance, I can't even imagine how much it would cost me as I had to go to he doctor's and have my arm x-rayed every two weeks and now I have to go to rehabilitation.
Last Saturday I went to the store and said that I wanted to speak to the manager to tell about my situation hoping some kind of apology and tell them they should be more responsible. They told me he was out and the person I talked to, told me that he was going to tell the store manager about this and make him/her call me. He also told me that the instructor we had that day was not their regular instructor. He was out for competition and that's why one of his friend covered for him. (So what? Is this a reason for being irresponsible and putting my life at risk?)
Anyway, I received no call from Boardriders. Instead they made the instructor call me the next day and he said he was sorry etc etc
I never thought a big and famous store like Boardriders would behave in such an irresponsible and careless way. The reason we subscribed was because we trusted Boardriders. I could have hit my head, I could have died. I don't want the same thing happen to another person, that's why I wanted to share my experience here. I am also considering taking some legal action about my situation and go to court. Any recommendations more than welcome.