How to abandon the mission? (Wolfenstein: Youngblood)

I went to the Brooder-3 is not fully bled. Now can not normally go forward, because sooner or later killing me and the mission starts from the beginning, or turn back, because in the tunnels under the Brooder-3 door from which I came is closed (in a room like mine with several floors). There are some options as to abandon the mission and return to side quests?