I'll try to explain the difference between смотреть and посмотреть by such examples. "Я смотрел на луну" approximately is translated as "I was looking at the moon" (we don't know if I am looking at the moon now, the action maybe is not complete). "Я посмотрел на луну" is tranlated as "I had looked at the moon" (action is complete) "Я смотрю на луну" is translated as "I am looking at the moon" (action is not complete) "Я посмотрю на луну" is translated as "I will look at the moon" (now I am not looking but maybe I will do it later)

Perfective aspect refers to a bounded single event, so you can translate 'смотреть' as 'to see, to look at', and 'посмотреть' as 'to have a look, to take a look'. As well as, for example: целовать -- to kiss, поцеловать -- to give a kiss, гулять -- to walk, прогуляться -- to take a walk etc etc...

1. - Что ты делал вчера вечером? - Смотрел фильм. (prosess) - Я посмотрел этот фильм. Могу вернуть диск. (result) 2. Я смотрел этот фильм 5 раз. (repeated action) Я посмотрел этот фильм. (once) 3. - У меня есть новый фильм! - Я уже смотрел его. (fact in the past. Result an how many times - not on question)

несовершенный вид (imperfect) is just.... 1. - English 'continuous' tenses 2. - Repeated or usual actions. ...somehow merged together. Whatever совершенный вид means (or rather 'feels' to Russian speaker) - we just NEVER use it in such cases.

How about "take a look" & "have a look" ?? I think it's the same what you are struggling with ;)