There is no stupid question. Keep it up.
To give you a better understanding, first, you need to know the meaning of Bù (不) mean no. You can use it when you want to reject something or deny, just like english.
For example, 1. do you want to hang out?Bù. 2.is she beautiful? Bù.
FYI, Bù (不) can combine with other word to make sentence more beautiful and meaningful. Bushi is one of those. Overall, if you use no to deny or reject something, I believe those who understand chinese will get what you mean.
Bùshì (不是)means is/am not. This is combination of 2 words. FYI,是mean yes.
You can use Bùshì when someone asks you:
are you 12 year old?
Are you from Italy?
For the above questions, you also can use Bù
I think you can learn better if you create more scenarios or sentence to use these words. We could correct you from your example.