How should I deal with a total nightmare of a person at work?

There is someone at my company who talks absolute nonsense constantly, like they have ADHD, and has a totally unrefined way of speaking, picking fights every now and then...
And they keep talking my ear off..
Even though I really want to avoid them, they follow me around everywhere.
What should I do? There is a large age gap, and I work at a company with no proper structure.
ㅠㅠ