In the new Betrayal DLC there are 4 new maps.
You must win heist on both teams on each of these 4 maps. Since Battlefield is a team game, it is hard to influence the outcome of the match by yourself and therefore you may have a little trouble winning on both sides.
Its likely after playing the maps a few times, you will win as one side, and lose on the other, or maybe you still need to win as both sides. I have a solution for both of those problems.
So let me give you an example:
I needed to win as the cops on Chinatown. I had already won as the criminals. So when Chinatown came around I would play through as the cops. If I lost, when the game switched sides, so that I was now a criminal, I would choose to become the hacker. Once you are the hacker there is an option to "Become the Enemy Teams Hacker" which can be done by pressing the "X" button. Once you are the enemy teams hacker, just resign from being hacker and you have effectively switched teams and have another chance to win as the cops.
If you come to a map where you need to win as both sides, you can try to switch when you have a good idea of which team is performing better using this hacker trick. So if you are playing Thin Ice and you need to win as criminals and cops, and the cops are 10 kills away from stopping the criminals, you should use the hacker trick to switch teams before the game ends and you will get the win.
If you have any questions or concerns, please let me know in the comments.