Basic contact form using React

What are you most proud of, and what would you do differently next time?

1. Practicing building basic react-powered form.
2. I should learn to use tailwind css for my styling.

What challenges did you encounter, and how did you overcome them?

1. Setting up and validating the error fields: I just figured it out.
2. The name fields being of two variables, firstName and lastName: I realised I had to create key and value pair seperately in my initialState object.
3. Styling was a bit weird for me, as I try to use a lot of helper classes but it ended up getting me confused. So in the end my code is a mashup of helper class style and generic css styling. I should learn to use tailwind, especially when working with react.

What specific areas of your project would you like help with?

Any areas requiring constructive critic. Also I wouldn't mind ideas to make the code more scalable and reusable.