got it working even more

system/dm.nix

@@ -1,18 +1,22 @@
-{ config, pkgs, lib, ...}:
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
 
 {
   services = {
     xserver = {
       xkb = {
-layout = "de";
-variant = "";
-};
-};
-displayManager.gdm = {
-enable = true;
-wayland = true;
-autoSuspend = false;
-};
-};
+        layout = "de";
+        variant = "";
+      };
+    };
+    displayManager.gdm = {
+      enable = true;
+      wayland = true;
+      autoSuspend = false;
+    };
+  };
 }
-

system/networking.nix

@@ -21,11 +21,3 @@
     };
   };
 }
-
-
-
-
-
-
-
-

system/shell.nix

@@ -3,13 +3,8 @@
 {
   environment = {
     systemPackages = with pkgs; [
-      fish
       coreutils
     ];
   };
-  # programs = {
-  #   fish = {
-  #     enable = true;
-  #   };
-  # };
+  programs.fish.enable = true;
 }