Hi Claudia,

I think that you need to study the various pronouns --  Subject, Direct / Indirect object, Reflexive.

Your query relates to reflexive pronouns which match the subject "person" of which there are three   --  I, you, him or her or it. singular and then the corresponding plural versions.

I recommend that you take each grammar element   - understand, practise, test.

In time you will become familiar with the various aspects of the grammar and will be able to progress.

Bonne continuation.

Jim