How do I play SIMPLE death match (free for all) in BF4 multiplayer?

This is not quake, teamwork is name of the game. The gamemode with most opponents and "only" up to 4 teammates is Squad DM. Looks like you wasted 70 Euro if All vs All is all you want to play.

If you bought it on Origin @ PC you can return it withing 24 hours of purchace no questions asked, see more here: https://help.ea.com/article/what-s-the-great-games-guarantee