Why is med used here?
In Swedish you have ’enough with something’.
How would one say: "I've had enough of something." ?
"Jag har fått nog av..."
Is it the same to say "Jag har fått nog av" or "Jag har tillräckligt med"? I mean, are the two options exactly the same? Can they be used any of them at any moment? Or do you use one or another in different situations?
No, they're very different.
Always? Is this a general rule?
Pretty much yes, unless you add a quantifier.
I was wondering where that accented e would come in.