Maaaan ! I really need to go to bed lol ! Thanks a lot !
Indeed case movies was totally messed up, helped me also find other stuff that wasn't right.
However, in the screen below is my new code now thanks to your help, but for example by going forward from the past exercice with the choice variable, I kept pressing enter hoping to get the "add" option, noob mistake !
Indeed when I wrote add instead of a movie title to display, then I could start with the case's inputs and finish.
A little suggestion to make it more clear for future students would be to add an extra step in the assignment to change the puts that gets the choice variable so that students change it to something like "what option do you want to select?", with then add etc in a string.