In Swedish people often confuse de/dem(they/them kind of) and I honestly don’t know exactly when to differentiate. You often learn to replace the word with another like vi/oss(we/us) to see if the sentence still sounds good and then you know the form you should use

How do you mean? Like cracking the knuckles or snapping the fingers?

Start with something specific, like a character or a setting and think about what it could be like. Sketch and get ideas on paper. It doesn’t have to be good but you have to start somewhere to learn what works and what doesn’t.

Bigger numbers are better than small numbers and I have no idea.