I can understand your confusion over these adverbs, because they do not have a one-to-one correspondence with other languages.
1. 'Already' is the equivalent of the Portuguese word 'já' in the sense of 'before now' or 'earlier than you thought'.
Do you want some lunch? I'm making a sandwich.
No, thanks, I've already had lunch.
Let's watch this movie.
No, I've already seen it. Let's watch something else.
2. 'Ever' is the equivalent of the Portuguese word 'já' in the sense of 'at any time'. You can use it to refer to unspecified time with any tense:
Have you ever been to New York?
(experiences in your life so far)
Do you ever see our old schoolfriend Jack these days?
(regular routines at the moment)
Will you ever move away from your home town?
(any time in the future)
3. 'Never' - 'nunca' in Portuguese - is the 'mirror image' of 'ever', in the same way that 'nobody' is the 'mirror image' of 'anybody'. For example:
I have spoken to nobody = I haven't spoken to anybody
I have never been to Africa = I haven't ever been to Africa
'Never' means 'at no time', while 'ever' means 'at any time'.
It's very easy. Don't worry!
Already = sooner than expected
Ever = at any time
Never = not at any time
You can check this in a regular dictionary.