[ expression of time + ago] I met her six weeks ago (NOT . . . ago six weeks.) It all happened a long time ago How long ago did you arrive?
Ago is used with a past tense, not the present perfect.
She phoned a few minutes ago. (NOT She has phoned . . .) 'Where's Mike?' 'He was working outside ten minutes ago.
The difference between ago and for
Compare: I went to Spain six weeks ago ( = six weeks before now) I went to Germany for six weeks this summer. ( = I spent six weeks in Germany.)
NOW I went I went to Germany to Spain PAST l-fl I M I I I I I I II I I II II f I I I I I I I I !-»? FUTURE for six weeks six weeks ago
The difference between ago and before
two years ago = two years before now two years before = two years before then (before a past time) Compare: Two years ago, I visited my home town, which I had left two years before. left , visited , NOW •-1--1-• _I two years ago two years before.