On this page of the guide to Wolfenstein: Youngblood there is a complete description of the battle with General Winkler, which is one of the main bosses of the game. Clash with General takes place in the final parts of the prologue campaign - during the main mission - Der-Nachtfalter.
To remind you, the mission of Der Nachtfalter takes place on board of a huge airship. The meeting with General Winkler will take place in the final part of the mission after he reaches the closed control room.
The General appears in the next room. After a brief monologue, he fires lasers at the sisters and the battle begins.
General Winkler uses the same disguise as the one provided by sisters' abilities. This means that he is not completely invisible. You just need to look more closely to see his silhouette. Shooting at General temporarily disables his disguise and allows you to attack him more easily.
Apart from standard attacks, the boss can shoot at sisters with lasers. They have a great killing power. If your sister is attacked, hide behind walls and other obstacles. If the second sister is attacked, use this to your advantage and attack Winkler.
During the fight in the lower control room, reinforcements may appear. Fortunately, these are weak opponents who can be easily killed.
If you need treatment, armor or ammo, then jump to the upper balconies. There you will find many useful supplies. And don't forget to help your sister if she falls to the ground and starts bleeding.
The final stage of the battle will move to the street. Attack Winkler until his health bar is depleted. The boss will lose his balance, but he will hold on to the airship's wing. Shoot Winkler, so he crashes into the engine and dies.