Brackey's Quiz Tutorial

Blitzit

Please, I need some help with this. Regarding a video about brackey's quiz game:

Link here: https://www.youtube.com/watch?v=5CW1yGsVg4k

I came across a slight dilemma towards the coding bit. At around 3:00 to 6:35 in the video, I'm always getting errors because when i put in

public Question[] questions;

// it always doesnt identify the Question class even though I stated it in the Question.cs script and I put serializable. Someone please help me out as I'm, doing this quiz game for my project.

When someone does figure out what to do, please reply back to this and tell me step by step what to do, or whether this is outdated and I have wasted my time. If I did waste my time, someone please give me an alternative on how to make a quiz game. Thank you so much