On the zero article 

In English we use the article "a" for jobs:
In English: "I am a teacher"
In Spanish: "I am teacher" (soy profesor). 

This also applies if you are talking about a specific job, religion or nationality.
"Soy inglés" (I am English), "es cristiano" (he is a christian), "eres profesor" (you are a teacher) 

It also applies to a thing in general. 
In English: "I do not have a car"
In Spanish: "No tengo coche" 
The car is general, you are not talking about a specific car. Just cars in general, and you don't have one.
"Soy mujer" - "I am a woman", not a specific woman in this case

Do not give up on Spanish, it is complex and very thorough, I know how you feel. I have struggled for over two years to even come close to B2, well before I started using this app. It is worth it though, keep it up!