You're doing a good job for a non-native speaker, Ignacio. But although "right" and "write" sound the same, they have two distinct meanings. "Right" is more complex and has several meanings, including one about legal rights, which is where the term copyright comes in. Those are the rights that writers (and other creators) have in their original works. To "write" is to generate script, orthographically speaking, or in your case copy for clients.