"Are you an engineer? Yes, I am"; "He is generous with me, and I am with him"; "He is my surety, and I am his"; must be translated by "Es V. ingeniero? Sí, lo soy"; "Es generoso conmigo y yo lo soy con él"; "Él es mi fiador y yo lo soy suyo."
=Past—=
The English language has one form of Simple Past—I wrote.
In Spanish this is translated by—
Yo escribía (Imperf. Indic.) or
Yo escribí (Past Definite), according to sense.
It is most important to learn the difference between the Imperfect Indicative and the Past Definite (or Preterite), because these two tenses admit of no compromise in Spanish.
The =Imperfect Indicative=[146] describes an action or state which was present when another past action took place, or another past state existed.
[Footnote 146: Or Descriptive Past.]
The =Past Definite= or =Preterite=[147] narrates an event.[148]