Have/had just & how long you have/had been doing something

Both the following constructions seem to demand a perfect or pluperfect tense in Spanish but they don't...   In fact, the pattern is as follows:

English   Spanish
Perfect tense > Present tense
Pluperfect tense > Imperfect tense
     
Have/had just Acabar de (+ infinitive)
I have just bought a new car Acabo de comprar un coche nuevo
We have just seen him Acabamos de verle
I had just arrived Acababa de llegar
They had just seen the film Acababan de ver la película
   
How long you have been doing something  
  (Verb) desde hace / desde hacía (length of time)
I have been studying Spanish for 5 years Estudio español desde hace cinco años
We had been waiting for them for half an hour Les esperábamos desde hacía media hora
  Hace/Hacía (length of time) que (verb)
I have been studying Spanish for 5 years Hace cinco años que estudio español
We had been waiting for them for half an hour Hacía media hora que les esperábamos
  Llevar (length of time) + present participle
I have been studying Spanish for 5 years Llevo cinco años estudiando español
We had been waiting for them for half an hour Llevaba media hora esperándoles