Should I spend the weekend with my grandmother?

Yes. I don't mean it bad, but you never know how long will they stay here with us.

yes, just let her do the talking if you dont know what to say

If she is a good cook, YES.

Yes. You never know how long you'll even have the option.
You may think you won't know what to do/say, but it will begin to flow naturally once you're hanging out with her. Just stay off your phone and let your social skills stretch a little. Ask her about her childhood, what she used to do for fun. How she met significant people in her life, funny or embarrassing stories about your parent. It will start to come naturally.