How to describe an action (past , present , future) in French ?

In French a specific expression is used to describe to action : "être en train de" whereas the English language uses perfect tenses (to be (past , present , future) + verb-ING) . Effectively no such tenses are existent in French . So the verb "être" needs to be conjugated depending on whether the action being described is happening in the present , was happening in the past or will be happening in the future . To describe an action being done now in the present , "être" is to be conjugated in the present tense as follows : "je suis/tu es/il,elle est/nous sommes/vous êtes/ils, elles sont en train de" . "J'étais/tu étais/il,elle était/nous étions/vous étiez/ils,elles étaient en train de" , which is "être" in the past simple tense , would be to describe an action that was being done in the past. And to describe an action that will be happening in the future , "to be" is to be conjugated in the future simple tense as follows : "je serai/tu seras/il,elle sera/nous serons/vous serez/ils,elles seront en train de" . Also in French leaving out "en train" is possible . In such case you may just conjugate the concerned verb . For instance "Qu'est-ce qui tu fais ?" (What are you doing right now?) , you may reply "je suis en train d'étudier" or "j'étudie" (I was studying) . Another instance would be "Qu'est-ce qui tu faisais quand je t'ai appelé?" (What were you doing when I phoned you?) , you may reply "j'étais en train de dormir" or "je dormais" (I was sleeping) . But here in the English language , relying "I studied" and "I slept" would not have been accurate.