Well, Spotify has admitted that there is problem with the App on Samsung S5.
I have a issue with them where they declared and announced the problem for this: read this thread: https://community.spotify.com/t5/Help-Android/samsung-s5-crashes/td-p/1218530/page/4
The only solution they helped me with is to download an older version of the app to get it to work, helpfully.
The app I downloaded takes about 3-4 minutes to get started, and trying to download offline-lists are absolutlly no idea.
I have asked for compensation but no answer on that request.