In American English, "I am here for a while" does not have the same meaning as "I have been here for a while." It means I am here now and will be for a while in the future. Maybe it's different in GB...?
Agreed, and the same in British English.. A better translation here would be 'I have been here for a while/spell'. The use of ers (since) implies that the action started in the past.
In Welsh, the present is used for things that have been going on for a while and are still continuing:
- Dyn ni'n byw yma ers blynyddoedd - We have lived here for years.
- Mae e'n gweithio yn Nhregaron er 1999 - He has worked in Tregaron since 1999
'I am here for a while' to me (in British English) sounds odd and would be is better expressed as, 'I will be here for a while' - Rydw/Bydda i yma am sbel. The use of am allows for a present/future meaning here, in contrast to er/ers.
Ah, at last, i could not get at this from the exercise. "For a while" seems much shorter than "for ages". To me, in English, this should be ' i was here for a while" past, yes, but not for ages!