I agree, however, in English, "she works at the gallery" may mean "she works for the gallery", depending on context. I would actually be much more likely to use "at" unless I specifically wanted to highlight that she worked for them but not necessarily at that site. The same would hold true for museums and certain other types of institution.
I already acknowledged that they don't mean exactly the same thing, however I struggle to think of a situation where I would prefer to say "works for the gallery" over "works at the gallery." I can just about make up a situation, but it is quite artificial because usually galleries have only one site. For companies, it is clearer "works for the bank", but for galleries, museums etc I would almost always say "at".
Here's an easy scenario: "She works 'for' the gallery (as an accountant/lawyer/designer/marketing consultant, etc...)." None of those jobs have to be done 'at' the gallery in question. She could have an office anywhere but work for the gallery.
On the other hand you could say the full time staff, e.g. the curator, receptionist, caretaker, security guard, etc, work "at" the gallery because more or less all their work depends on being there.
I hope that clarifies the meaning of the previous comment. I wasn't trying to put-down or anything.
It often is. There are two situations.
A. Contraction with definite article:
para a -> pra, para o -> pro, para as -> pras, para os -> pros
These are acceptable in all situations, I believe.
B. Informal contraction. Here, "para" is just replaced by "pra". This is a recognised language form (appears in dictionaries etc), but only (I think) in Brazilian Portuguese. It is only suitable in the informal register: in spoken language or when writing is specifically trying to be informal. It is what I hear most often when speaking to Brazilian friends, but I can't comment on whether it is broadly the more common spoken variant.
I've seen it in songs and brazilian news (Folha TV). Especially MPB. for instance Seu Jorge's final line to chega no suingue chega pra ca' Yeah, I have never seen it in continental ptg. It's strange that these contractions have not spread as similar linguistic changes have in eng. Like do not ---> don't. but there are some like voce -->vc or ce' I do hear the vowels elide when they are consecutive in sentences, but that's not contraction.