Hello, I am a Spanish speaker and would like to help you. In this problem, we need to use correctly two important verbs in Spanish: ser and estar.
We use the verb ser to talk about permanent or lasting attributes. In this way, this verb stands for <em>descriptions, occupations, characteristics, time, origin and relationships. </em>
On the other hand, we use the verb estar to indicate temporary states and locations. In this way, this verb stands for <em>position, location, action, condition, and emotion.</em>
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So, solving this problem we have:
1. Daniel está hablando por teléfono con su primo Ernesto.
In this case, it is used the conjugation of verb estar for the third-person singular (él - he). This sentence points out an <em>action, </em>that is, the verb is used to describe an ongoing action, the action of talking on phone.
2. Ernesto está deprimido
In this case, it is used the conjugation of verb estar for the third-person singular (él - he). This sentence points out an <em>emotion, </em>so we are expressing what Ernesto is feeling at that moment, that is, he is depressed.
3. Porque su novia está muy lejos
The reason why Ernesto is depressed is because his girlfriend is far away. In this case, it is used the conjugation of verb estar for the third-person singular (ella - she).
4. Ella está en los Estados Unidos
She is in USA. It is also used the conjugation of verb estar for the third-person singular (ella - she).
5. Su situación es complicada
In this case, it is used a conjugation of verb ser. This sentence points out a<em> relashionship, </em>so their relationship is very complex
6. Porque Ernesto es de México
In this case, it is used the conjugation of verb ser for the third-person singular (él - he). This sentence points out an <em>origin. </em>So, we can consider as an origin the place a person or thing is from. Therefore, Ernesto is from Mexico.
7. y su novia es estadounidense y vive en Miami
This sentence points out that Ernesto's girlfriend is from USA.
8. Ellos están muy enamorados
In this case, it is used the conjugation of verb estar for the third-person plural (ellos - they). This sentence points out a <em>relationship. </em>They are so in love
9. Pero no están felices
In this case, it is also used the conjugation of verb estar for the third-person plural (ellos - they). They are not happy.
10. Ernesto está pensando en ir a estudiar a Miami
In this case, it is used the conjugation of verb estar for the second-person singular (él - he). This sentence points out an <em>emotion. </em>Ernesto is thinking about going to study in Miami
11. y le pregunta a su primo Daniel si es una buena idea. ¿Qué consejos le dará Daniel a su primo?
Finally, here it is used a conjugation of the verb ser.
