Spanish is not the language you want to learn right now. But the following chapters are based on what is written here, so it is a good idea two spent two minutes reading it.
We already said that the difference between essere and stare has nothing to do with the difference in Spanish between ser and estar. Let's see what is the difference in Spanish. Both verbs mean to be, but estar describes an epheremal characteristic and ser an inherent characteristic.
Las fresas están verdes todavía. = The strawberries are already green.
Las fresa son rojas. = The strawberries are red.
Green is, concerning strawberries, an ephemere characteristic, because normally they are red.
To this rule there is an important exception. Everytime you can use to stay instead of to be (He is in Madrid <=> He stays in Madrid) you use estar in Spanish.
He is in Madrid.
He stays in Madrid.
Está en Madrid.
Beside that there are other important exceptions to the basic rule. The most famous is this one.
Él está muerto.
He is dead.
Dead is definitely not an ephemeral characteristic. It is very definitive. Nevertheless in this context we use estar. But we can say that more ore less 90 per cent of the cases follows the two basic rules mentioned before and ser and estar are never interchangeable. That's not the case in Italian.
The next difference concerns the passive voice. We already know that in some languages, but not in English, there are two different forms of passive voice.
description of the result of a proces: The car is repaired.
description of the process itself: The car is being repaired (at the moment).
In English there is no special verb to describe a process. If it is important to distinguish between a state and a process. If it is really important to make clear that the stress is on the process, the continuos form has to be used.
In Spanish the state passive voice is formed with estar the process passive voice with ser.
passive voice of state: Él ha sido bautizado. = He was baptized.
passive voice of process: Él ha estado bautizado. = He was being baptized.
That' s completely different in Italian. The PASSIVE VOICE that describes a STATE (the result of a process => The car was bought) ist formed with essere, the passive that describes a process (the process itself => The car was being bought) with venire. If the context allows to deduce whether it is a passive voice of state or a passive voice of process essere can be used as well to describe a process.
passive voice of process: Lui venne battezzato. = He was being baptized.
passive voice of state: Luifubattezzato. = He was baptized.
Essere and stare have the same past participle: stato. Both are conjugated with essere. In other words in the compound tenses they have the same form. Therefore there is no need in the compound tenses to ask onself whether to use essere or stare.
conjugation essere / stare - indicativo
io sono stato
tu sei stato
lui è stato
noi siamo stati
voi siete stati
loro sono stati
io ero stato
tu eri stato
lui era stato
noi eravamo stati
voi eravate stati
loro erano stati
io sarò stato
tu sarai stato
lui sarà stato
noi saremo stati
voi sarete stati
loro saranno stati
conjugation essere / stare - Congiuntivo
io sia stato
tu sia stato
lui sia stato
noi siamo stati
voi siate stati
loro siano stati
io fossi stato
tu fossi stato
lui fosse stato
noi fossimo stati
voi foste stati
loro fossero stati
io sarei stato
tu saresti stato
lui sarebbe stato
noi saremmo stati
voi sareste stati
loro sarebbero stati
The main difference between essere / stare in Italian and ser / estar in Spanish is this: In Spanish ephemeral emotions (He is nervous, He was surprised, He was happy) are described with estar. It is compulsory to see that emotions are NEVER described in Italian with essere, whether the emotion is an inherent characteristic or a ephemeral emotion. We are going to discuss that in detail later.