This sentence was written to me by Spanish native from Madrid:
"Lo primero disculparme por no haberte podido escribir en el mismo día"
I completely understand the meaning of it. But have some misunderstandings in terms of grammar. So 3 questions:
"disculparme" - Am I correct that it is reflexive verb of disculparse? At first I thought it should be imperative "discúlpame", but then I thought what this person meant that she is not asking me to forgive her, but rather she figuratively "forgives herself". In English it would be "I apologise", but not "forgive me".
"por no haberte podido escribir" - how is it formed? What tense is it? Feels to me like an idiom. At least I would never be able to form this myself logically before.
"En el mismo día" - shouldn't it be just "El mismo día"?