The Spanish word pareja means two different things and yes, one of them is couple.
But couple refers to two things seen as ONE UNIT.
I went out with a couple (un par) of friends.
Leo has a couple of dogs.
If you’re talking about the one person you share your life with, that is the other meaning of pareja, your partner.
I went out with my partner. (NOT I went out with my couple.)
She has a partner. (NOT She has a couple. A couple of what?)
I hope that’s clear!