How can I know that "Bordeaux" is feminine?

Are you sure that it is ?

See the link for previous comments on this topic by Cécile

https://progress.lawlessfrench.com/questions/view/do-city-names-have-gender

Also, for more discussion, see this external link. 

https://www.frenchtoday.com/blog/french-grammar/paris-est-beau-belle/

Personally, I wouldn't sweat it too much, it is not a major issue in most situations.

hi team - in the lesson there are two examples that I am not sure I understand

1.  Michael vient de Quebec

2.  Mon petit amie vient du Quebec 

are both correct - I am confused 

hi team - in the lesson there are two examples that I am not sure I understand

1.  Michael vient de Quebec

2.  Mon petit amie vient du Quebec 

are both correct - I am confused 

The lesson explains that ‘Québec’ is the name of a province in Canada, and it is also also the name of a city in the province.

1. the province is masculine grammatically, takes an article, so that it is actually ‘le Québec’ (and it behaves grammatically as a country) - hence ‘venir de le Québec’ contracts to ‘ venir du Québec’, and ‘la petite amie’ comes from the province of Québec  (city or town etc left unspecified)

 2 The city of Québec, like most cities and towns takes no article, and therefore ‘venir de’ doesn’t change - Michael comes specifically from the city of Québec . 

This is difficult to ‘absorb’ because the definite article in this context only comes into consideration for the minority of countries that are masculine or plural grammatically - it is all there in the lesson though.