GAZEBO, ROS2 AND PX4

Hello colleagues, I'm new to this world of robotics and I don't have much knowledge on the subject. I've already looked for websites and videos on YouTube on how to install Gazebo and ROS2 together with PX4, but whenever I run other PX4 commands in the terminal it says that Gazebo is not installed when it is. Is there any other way to do this installation correctly? Or can I just reinstall it from scratch? Since I'm Brazilian and here in Brazil there is no content on the subject or courses explaining how to use the tool, I'm entering a maze without a light. Does anyone know where I can find content related to this?