🔼WAS/ WERE GOING TO - WAS/WERE SUPPOSED TO🔽

Function:

1. We use going to in the past to talk about plans and intentions that didn’t happened.
2. We use supposed to in the past to talk about things we were expected to do that we didn’t do. 

Form:

Was/were going to + base form	-Was going to pay for them. -I was going to see what they looked like in daylight.
Was/were supposed to + base form	-You were supposed to for them before you left the store.

➽ 1.- Was/ were going to + base form: 

It is formed with the verb 'to be' in the past, followed by 'going to' and then the main verb

AFFIRMATIVE: To form the affirmative we put the corresponding form of the verb 'to be' accompanied by 'going to' and a verb.

Sujeto + was/were + going to + verbo + resto de frase.

They + were + going  to + dance in a party. (Ellas iban a bailar en una fiesta).

Examples:

1. I was going to see you tomorrow. (Yo iba a verte mañana)
2. He was going to visit her next week. (Él la iba a visitar la siguiente semana)
   
3. They were going to eat out tonight. (Ellos iban a comer fuera esta noche)
   
4. She was going to leave for Europe on Monday. (Ella iba a partir a Europa el lunes)
5. She was going to wait me after the show. (Ella iba a esperarme después del espectáculo)

➽ 2.- Was/ were supposed to + base form:

 

We will use was / were supposed to talk about things that we agreed to do, or that people expect us to do, but we did not.

Examples: 

1. He is supposed to take his dance lesson at seven o’clock. (Se supone que él toma su clase de baile a las siete en punto)
   
2. They were supposed to bring the books with them. (Se supone que ellos traen los libros con ellos)
   
3. He is supposed to arrive tomorrow. (Se supone que él llega mañana)
4. You are supposed to be here after four o’clock. (Se supone que tú estás aquí después de las cuatro en punto)
5. We are supposed to send them a letter. (Se supone que nosotros les enviamos una carta)

Exercices:

Complete the sentences with was / were going to / was / were supposed to.

1. I was standing in line and I _____________ buy the Inception DVD, but I decided to put it down because I needed to save money.

   2.  I don't _____________________________ you could lend me some money, could you?

  3. I am not _____________________________ smoke here.This is a place for children.

   4.  _____________________________ you won the lottery, what would you buy?

  5.  I _____________________________ it will snow. Don't go out without a warm jacket.

🔼SHOULD/ SHOULDN´T HAVE🔽

_____________________________________________

Function: 

We use the perfect modal should / shouldn`t have to criticize or express regret about things that people did or didn`t do in the past.

Structure:

Should have + Past participle	I / he / She / We / you / they should have gone to the doctor.
Shouldn`t have + Past participle	I / he / She / We / you / they shouldn`t have been rude to the store assistant.

➽ SHOULD HAVE 1: Should have + past participle. 

1. We can use 'should have' to talk about past events that did not happen.
2. We can also use 'should have' to speculate about events that may or may not have happened.

Grammar:

It may mean something that would have been a good idea, but that you did not. It's like giving advice about the past when you tell someone else, or regretting what you did or did not do when you're talking about you.

Examples: 

1. She should have taken the children with her to Houston. (Ella debería haber llevado a los niños con ella a Houston)
   
2. He should have lent us the money which we need. (Él debería habernos prestado el dinero que necesitamos)
   
3. She should have been back by noon. (Ella debería haber regresado para mediodía)
4. She should have returned later. (Ella debería haber regresado más tarde)
5. You should have learnt at least five new words every day. (Tú deberías haber aprendido al menos cinco palabras cada día)

➽ SHOULDN'T HAVE 2: Shouldn't have + past participle. 

It means that something was not a good idea, but you did it anyway.

Grammar:

1. We can use 'shouldn't have' to speculate negatively on what may or may not have happened.
2. We can also use 'shouldn't have' to regret past actions.

Examples: 

1. You should not go by plane. (Tú no deberías ir en avión)
2. He should not save some money each week. (Él no debería ahorrar algo de dinero cada semana)
3. He should not pay more attention to what the teacher says. (Él no debería poner más atención a lo que dice el maestro)
   
4. It should not rain this evening. (No debería llover esta tarde)
   
5. We should not ask permission before doing it. (Nosotros no deberíamos pedir permiso antes de hacerlo)

➽ Exercices:

 Read these prayers of repentance and write the correct past participle verb:

• 1) I should have (buy) more water.
• 2) You should have (listen) to me.
• 3) I should not have (forget) my passport.
• 4) He should have (wear) a tie to the restaurant.
• 5) I should not have (eat) so much.
• 6) We should not have (drive) during the storm.
• 7) You should not have (hide) your sister's phone.
• 8) I should have (do) more research.
• 9) She should not have (drink) so much wine.
• 10) I should have (write) more.

For more information check the video link to clarify your doubts about the subject, thank you.