Artificial Intelligence is an umbrella term. Machine Learning is a subset of Artificial Intelligence and Deep Learning is a subset of Machine Learning. Before going into further in these fields you should learn Python programming language. So, the order in which you should learn these fields are:
If I talk about Natural Language Processing then it's a part of these fields. So, while covering the concepts in these fields you will learn all about NLP.
If you are a beginner go through this blog to know more about AI:
Also, if you want to learn AI from scratch you must go through this tutorial:
For getting a job as an AI engineer you should be a professional in AI and you need to have a certificate for proving it, so, you should go for Artificial Intelligence Online training to make your career rise to the next level.