API Plataform: Rest resource name + Class does not exists error

Question

I am trying my first steps with Symfony 4 and API Platform to create a real simple API but, I am getting troubles with two points:

1) I don't know/understand why the Resource Name from my Entity is getting the first letter removed + it's adding plural in the end

2) When I try the request using Postman I get the error message below:

I feel that I am really missing some point and extra info... It can't be that complicate...

Thanks for any help guys!