Verb types...part 1 (maybe)

I’ve been using Gramática Activa 1 (for estrangeiros) to help me with some of the grammar aspects of the language. Here’s what I’ve come to understand about verbs so far. This is by no means complete (I haven’t even started the conditional/future, etc.). Indeed, nor is it correct. Indeed - please correct my statements below.

Present - what’s happening now

Preterit - what happened in the past where:

  • a discrete one-time completed action

Imperfect - what happened in the past where (and this is where it gets interesting):

  • Repetitive, habitual actions; no longer in progress
  • Simultaneous/concurrent past actions
  • courtesy requests (use 3rd person - queria, gostava, preferia… )
  • past habitual actions that have changed (use imperfect of costumar + infinitive of auxiliary)
    ** Eu costumava ir para pé, agora vou para autocarro.

Mixed Use:
Past sequential actions (I had action1 then action 2)
Ter (conjugated in imperfect) + the past participle for the 1st action, preterit for action 2
I had gone to the store then I bought food
Tinha ido na loja então comprei comida

Actions started in the past continuing to the present
Ter (conjugated in the present) + the particple
I have been sick
Eu tenho estado doente