"Irregular verbs are common verbs in the English language that do not follow the simple system of adding “d” or “ed” to the end of the word to form the past tense. That means the spellings can be a little tricky. Some irregular verbs follow patterns, such as drink–drank, spring–sprang, know-knew, and blow-blew but you can’t use those patterns with predictability. Unfortunately, learning irregular verbs means memorization."

http://www.k12reader.com/irregular-verbs/

UNIT 2

The present perfect it's used when we want to say that an action happened at an unone time before now. And the exact time it's not impotant.

UNIT 1

The active voice is used when the subject performs denoted by the verb

And the passive voice is the one that changes the normal word order, that way the subject is no longer active, but being acted upon by the verb 

I need to have done by tomorrow my PowerPoint presentation about my greatgreatfather.

Phrasal verbs sometimes have a literal meaning and sometimes an idiomatic meanning.