S'il vous plaît (it sounds kind of weird here, either move it to the end of the sentence, after 'fruit', or change it to something like 'excusez-moi') je ne veux pas manger de poisson, je veux un fruit. (or 'des fruits')

No, it's not correct. Grammar aside, you have some serious spelling problems: 1. veux, NOT veix 2. manger, NOT mange 3. vous, NOT vou