I've read that Poles have a mentality of victimhood and defensiveness about there country and history. Is any of that true?
What are Poles taught and think about the Anglo-French war guarantee if Poland was invaded by Germany?
Yes, it's partly true. I've heard about some serious scholars discussing if Poland has "post-colonial trauma", just like the African states

Well, about the guarantees, not much is said, but obviously, the 'strange war', and british-american unwillingness to help Poland retain its eastern territory and independance, as well as opposition to Poland acquiring much territory in the west, is often recalled. In general, there used to be a tradition of talking about the "treason of the West". Of course, during the communist times it had a political significance and support. It's not alive now, though, because, especially during the 90's, the West was idealised.
Have you ever been to Posen? Does it still retain any sign of having once been a German province?
Well, I've been to Poznan, obviously. If you mean Posen (Major Poland) as a province, its citizens are seen as tidy, accurate, overly organised and stingy. sort of like Germans.
There's a population called Bambrzy around Poznan (although my friends from Poznań tell me "Bamber" is also a slur). They came originally (in XVIII century, before german rule) from the town of Bamberg in Germany, they retain unique folklore, but they speak polish only, even if they have German surnames. The most reknown of them was archbishop Paetz, who was forced to resign after a sexual scandal. But, again, they came before german rule and are completely polonised, although aware of their german origin.
There's no significant germany minority there anymore. Definite most left Major Poland after Poland regained independance, after ww1. They were nominally quite numerous before (up to 40%, but including the bits that Poland didn't gain after ww1), but mostly due to XIX century sponsored immigration and forced assimilation.
oh, and warpus, be my guest.