diff --git a/src/g2_2025_grade_calculator_pkg/CMakeLists.txt b/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
index feeda54..2510274 100644
--- a/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
+++ b/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
@@ -8,14 +8,27 @@ endif()
 # find dependencies
 find_package(ament_cmake REQUIRED)
 find_package(rclcpp REQUIRED)
+find_package(g2_2025_interfaces REQUIRED)
 
-add_executable(grade_generator src/main.cpp)
+add_executable(exam_result_generator src/exam_result_generator/main.cpp)
+add_executable(final_grade_determinator src/final_grade_determinator/main.cpp)
+add_executable(grade_calculator src/grade_calculator/main.cpp)
+add_executable(retake_grade_determinator src/retake_grade_determinator/main.cpp)
+add_executable(retake_scheduler src/retake_scheduler/main.cpp)
 
-ament_target_dependencies(grade_generator rclcpp)
+ament_target_dependencies(exam_result_generator rclcpp g2_2025_interfaces)
+ament_target_dependencies(final_grade_determinator rclcpp g2_2025_interfaces)
+ament_target_dependencies(grade_calculator rclcpp g2_2025_interfaces)
+ament_target_dependencies(retake_grade_determinator rclcpp g2_2025_interfaces)
+ament_target_dependencies(retake_scheduler rclcpp g2_2025_interfaces)
 
 install (
     TARGETS
-        grade_generator
+        exam_result_generator
+        final_grade_determinator
+        grade_calculator
+        retake_grade_determinator
+        retake_scheduler
     DESTINATION lib/${PROJECT_NAME}
 )
 
diff --git a/src/g2_2025_grade_calculator_pkg/package.xml b/src/g2_2025_grade_calculator_pkg/package.xml
index 9f7f271..31cb72c 100644
--- a/src/g2_2025_grade_calculator_pkg/package.xml
+++ b/src/g2_2025_grade_calculator_pkg/package.xml
@@ -10,6 +10,7 @@
   <buildtool_depend>ament_cmake</buildtool_depend>
 
   <depend>rclcpp</depend>
+  <depend>g2_2025_interfaces</depend>
 
   <test_depend>ament_lint_auto</test_depend>
   <test_depend>ament_lint_common</test_depend>
diff --git a/src/g2_2025_grade_calculator_pkg/src/main.cpp b/src/g2_2025_grade_calculator_pkg/src/exam_result_generator/main.cpp
similarity index 100%
rename from src/g2_2025_grade_calculator_pkg/src/main.cpp
rename to src/g2_2025_grade_calculator_pkg/src/exam_result_generator/main.cpp
diff --git a/src/g2_2025_grade_calculator_pkg/src/final_grade_determinator/main.cpp b/src/g2_2025_grade_calculator_pkg/src/final_grade_determinator/main.cpp
new file mode 100644
index 0000000..7279717
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/src/final_grade_determinator/main.cpp
@@ -0,0 +1,40 @@
+/* node_template.cpp
+ * Action server node template for ROS2
+ *
+ * Node description:
+ * Template action server that demonstrates action server implementation
+ * with goal handling, feedback publishing, and cancellation support
+ *
+ * Reviewed by: <x>
+ * Changelog:
+ * [04-09-2025] Wessel T: Implement template
+ */
+
+#include <cstdlib>
+
+#include "rclcpp/rclcpp.hpp"
+
+namespace lessons::zero::tmp {
+
+class NodeTemplate : public rclcpp::Node {
+public:
+    NodeTemplate()
+    : Node("node_template")
+    {
+    }
+
+private:
+};
+
+} // namespace lessons::zero::template
+
+int main(int argc,char *argv[]) {
+    rclcpp::init(argc,argv);
+
+    auto node = std::make_shared<lessons::zero::tmp::NodeTemplate>();
+
+    rclcpp::spin(node);
+    rclcpp::shutdown();
+
+    return 0;
+}
diff --git a/src/g2_2025_grade_calculator_pkg/src/grade_calculator/main.cpp b/src/g2_2025_grade_calculator_pkg/src/grade_calculator/main.cpp
new file mode 100644
index 0000000..7279717
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/src/grade_calculator/main.cpp
@@ -0,0 +1,40 @@
+/* node_template.cpp
+ * Action server node template for ROS2
+ *
+ * Node description:
+ * Template action server that demonstrates action server implementation
+ * with goal handling, feedback publishing, and cancellation support
+ *
+ * Reviewed by: <x>
+ * Changelog:
+ * [04-09-2025] Wessel T: Implement template
+ */
+
+#include <cstdlib>
+
+#include "rclcpp/rclcpp.hpp"
+
+namespace lessons::zero::tmp {
+
+class NodeTemplate : public rclcpp::Node {
+public:
+    NodeTemplate()
+    : Node("node_template")
+    {
+    }
+
+private:
+};
+
+} // namespace lessons::zero::template
+
+int main(int argc,char *argv[]) {
+    rclcpp::init(argc,argv);
+
+    auto node = std::make_shared<lessons::zero::tmp::NodeTemplate>();
+
+    rclcpp::spin(node);
+    rclcpp::shutdown();
+
+    return 0;
+}
diff --git a/src/g2_2025_grade_calculator_pkg/src/retake_grade_determinator/main.cpp b/src/g2_2025_grade_calculator_pkg/src/retake_grade_determinator/main.cpp
new file mode 100644
index 0000000..7279717
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/src/retake_grade_determinator/main.cpp
@@ -0,0 +1,40 @@
+/* node_template.cpp
+ * Action server node template for ROS2
+ *
+ * Node description:
+ * Template action server that demonstrates action server implementation
+ * with goal handling, feedback publishing, and cancellation support
+ *
+ * Reviewed by: <x>
+ * Changelog:
+ * [04-09-2025] Wessel T: Implement template
+ */
+
+#include <cstdlib>
+
+#include "rclcpp/rclcpp.hpp"
+
+namespace lessons::zero::tmp {
+
+class NodeTemplate : public rclcpp::Node {
+public:
+    NodeTemplate()
+    : Node("node_template")
+    {
+    }
+
+private:
+};
+
+} // namespace lessons::zero::template
+
+int main(int argc,char *argv[]) {
+    rclcpp::init(argc,argv);
+
+    auto node = std::make_shared<lessons::zero::tmp::NodeTemplate>();
+
+    rclcpp::spin(node);
+    rclcpp::shutdown();
+
+    return 0;
+}
diff --git a/src/g2_2025_grade_calculator_pkg/src/retake_scheduler/main.cpp b/src/g2_2025_grade_calculator_pkg/src/retake_scheduler/main.cpp
new file mode 100644
index 0000000..7279717
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/src/retake_scheduler/main.cpp
@@ -0,0 +1,40 @@
+/* node_template.cpp
+ * Action server node template for ROS2
+ *
+ * Node description:
+ * Template action server that demonstrates action server implementation
+ * with goal handling, feedback publishing, and cancellation support
+ *
+ * Reviewed by: <x>
+ * Changelog:
+ * [04-09-2025] Wessel T: Implement template
+ */
+
+#include <cstdlib>
+
+#include "rclcpp/rclcpp.hpp"
+
+namespace lessons::zero::tmp {
+
+class NodeTemplate : public rclcpp::Node {
+public:
+    NodeTemplate()
+    : Node("node_template")
+    {
+    }
+
+private:
+};
+
+} // namespace lessons::zero::template
+
+int main(int argc,char *argv[]) {
+    rclcpp::init(argc,argv);
+
+    auto node = std::make_shared<lessons::zero::tmp::NodeTemplate>();
+
+    rclcpp::spin(node);
+    rclcpp::shutdown();
+
+    return 0;
+}
diff --git a/src/g2_2025_interfaces/CMakeLists.txt b/src/g2_2025_interfaces/CMakeLists.txt
new file mode 100644
index 0000000..9bb5c01
--- /dev/null
+++ b/src/g2_2025_interfaces/CMakeLists.txt
@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.8)
+project(g2_2025_interfaces)
+
+if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  add_compile_options(-Wall -Wextra -Wpedantic)
+endif()
+
+# find dependencies
+find_package(ament_cmake REQUIRED)
+find_package(rosidl_default_generators REQUIRED)
+
+rosidl_generate_interfaces(${PROJECT_NAME}
+    "msg/Student.msg"
+    "msg/Exam.msg"
+    "srv/Exam.srv"
+    "action/Retake.action"
+)
+
+ament_export_dependencies(rosidl_default_runtime)
+
+ament_package()
diff --git a/src/g2_2025_interfaces/action/Retake.action b/src/g2_2025_interfaces/action/Retake.action
new file mode 100644
index 0000000..66ebe9a
--- /dev/null
+++ b/src/g2_2025_interfaces/action/Retake.action
@@ -0,0 +1,5 @@
+string student_name
+string lecture_name
+---
+---
+float32 result
diff --git a/src/g2_2025_interfaces/msg/Exam.msg b/src/g2_2025_interfaces/msg/Exam.msg
new file mode 100644
index 0000000..63d87a2
--- /dev/null
+++ b/src/g2_2025_interfaces/msg/Exam.msg
@@ -0,0 +1,2 @@
+string lecture_name
+float32 result
diff --git a/src/g2_2025_interfaces/msg/Student.msg b/src/g2_2025_interfaces/msg/Student.msg
new file mode 100644
index 0000000..566c1cc
--- /dev/null
+++ b/src/g2_2025_interfaces/msg/Student.msg
@@ -0,0 +1,2 @@
+string student_name
+string lecture_name
diff --git a/src/g2_2025_interfaces/package.xml b/src/g2_2025_interfaces/package.xml
new file mode 100644
index 0000000..e596ef9
--- /dev/null
+++ b/src/g2_2025_interfaces/package.xml
@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+<package format="3">
+  <name>g2_2025_interfaces</name>
+  <version>0.0.0</version>
+  <description>TODO: Package description</description>
+  <maintainer email="wessel@todo.todo">wessel</maintainer>
+  <license>TODO: License declaration</license>
+
+  <buildtool_depend>ament_cmake</buildtool_depend>
+
+  <build_depend>rosidl_default_generators</build_depend>
+  <exec_depend>rosidl_default_runtime</exec_depend>
+  <member_of_group>rosidl_interface_packages</member_of_group>
+
+  <test_depend>ament_lint_auto</test_depend>
+  <test_depend>ament_lint_common</test_depend>
+
+  <export>
+    <build_type>ament_cmake</build_type>
+  </export>
+</package>
diff --git a/src/g2_2025_interfaces/srv/Exam.srv b/src/g2_2025_interfaces/srv/Exam.srv
new file mode 100644
index 0000000..8e9945c
--- /dev/null
+++ b/src/g2_2025_interfaces/srv/Exam.srv
@@ -0,0 +1,5 @@
+# Request
+string student_name
+string lecture_name
+---
+float32 result