Eventually, someone is going to steal your content. It’s not a question of “if”, it’s a question of “when”.
The first thing you should do is ask them to take it down. Sending them an email to notify them that they need to remove it is the first step.
Most of the time, just shooting them an email will solve this. Almost every takes it down.
As for the scraper sites that steal your content, you can ignore them. Google knows about these sites and they don’t hurt your rankings.
As for duplicate content, Google doesn’t penalize for duplication. So you don’t have to worry about your rankings dropping.
And when people borrow parts of your content and they cite you, just leave it as is. Reason being is they tend to link back to your site as they cite information from your website. This helps rankings.
If you really want someone to remove your content you can get lawyers involved but it typically isn’t worth the cost.
If someone doesn’t remove my content after I email them, I typically just leave it as is and ignore it.