The Final Reich is the first Nazi Zombie map in Call of Duty WWII. Unlike past zombie maps in Call of Duty games, this map has a series of objectives that appear in the corner of the screen. In the past, these were often hidden objectives that took some work to figure out. Most of these objectives are easy to understand, but as you progress some of these can be a little obscure. Completing these quests will eventually lead you to the end of the map.
Like a lot of objectives in past, you will need to kill zombies in order to get points before you can unlock the doors needed to progress to the areas needed in order to complete the objectives. It might seem easier that this game will tell you the objectives, but there are a LOT of them compared to past games. Simply surviving this many waves is enough of a challenge without needing to complete the objectives at the same time.
The video guide below will show you how to complete all of the objectives required to get to the end of the Final Reich zombies map in Cod: WWII. Completing this will unlock the fireworks achievement/trophy. Once you have completed it there are some further things that you can do to unlock an alternate ending if you want to be a completionist and get a diferent trophy/achievement, but it will require you do this again with some different steps to change the final outcome.