I missed that typo - *class USptingArmComponent ** in Header1.h should be *class USpringArmComponent **.
You got errors half-way through the video when you removed the USpringArmComponent property because you left the “UPROPERTY(” line which needs a variable declaration to go with it (also take out the UPROPERTY line that is after the comment /**.Follow Camera */).
The function ACharacterAI::OnSeePawn(APawn* Pawn) error:
AControllerAICharacter* Controller = Cast<AControllerAiCharacter>GetController());
should be:
AControllerAICharacter* Controller = Cast<AControllerAiCharacter>(GetController());
Errors that have a Code starting with “LNK” mean they are linker errors instead of compile errors. This means after compiling, trying to link code to other code did not work. Trying to double click on these will not take you to the place of cause as the errors are located in the compiled obj files. A linker error generally happens when you are including a header file without cpp implementation (generally the cause is a function that hasn’t been defined in the cpp file but is declared in the header file).
The error at the end of the first video was likely the fact you removed the OnSeePawn function from ACharacterAI in the cpp file but the function declaration still existed in the header file.
I’m sorry to say but this is very much a lack of ability to understand basic programming to be able to notice and resolve typo errors. I will try and help you get this build going but I really don’t see you being able to continue writing code for UE4 without first doing structured learning if you cannot detect and solve these kinds of problems yourself (as all programmers end up with much harder errors they have to deal with as their project grows).
If this is not your code and is someone else’s code that you copy-pasted or got from a plugin, you should ask them to fix their errors if you are finding any errors being stated in their source files by UE4 or Visual Studio.