It sounds like you didn’t learn the information sufficiently enough before making them into cards. Anki isn’t good for teaching you new things, it’s good for remembering stuff that you already know - or are at least familiar with.

As the other responder said, don't use Anki for memorization, only for reviewing what you already remember. I recommend using mnemonics for memorizing words. For katakana hiragana, refer to https://www.tofugu.com/japanese/learn-hiragana/