I'll fix your question first: Hey, I have a question: does "my grandmom could speak fıve languages" mean in the past? I mean, why not "my grandmom can speak five languages"? Could is past tense; perhaps my grandmother is now dead or maybe she was able to speak five languages a long time ago. (Don't use "wanna" in your writing. Ever.) OK, there are a few possibilities: 1) Your grandmother passed away years ago. When she was alive, she could speak five languages. 2) Your grandmother is still alive, but very old and senile. When she was younger, she could speak five languages. She has now forgotten how to. 3) Your grandmother is alive and lucid, and she has a talent for languages. However, she does't develop it much. If she made the effort, she could speak fıve languages (instead of only two or three). This is the Second Conditional pattern.

I know what's your question. You want to know why use 'could' but 'can' in this sentence, and what's 'could' stand for. 'Could' is past tense of can in this sentence.