Thanks for reaching out about this here in the Community.
At the moment, it's not possible to message another Spotify user within the app.
You can have a look in our Idea Exchange to see if someone else has already made a similar suggestion. If there isn't one, you can give these steps a go and submit your idea so that other users can also support it. The higher the number of votes an idea gets, the more likely it is for it to be implemented.
Hope this helps. Let us know if you have any questions.
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.
“Music acts like a magic key, to which the most tightly closed heart opens.”– Maria von Trapp