My principal doubt is, if Girona after this international break is gonna still being this good, or they are gonna start to fall behind, maybe they can last until the winter break, and become the winter champions

i remember the alst team becoming winter champion asides of the big threes was Real Sociedad a lot of time ago.
Valencia has also been champion of the Spanish League and that's been a long time, Girona continues to amaze people, the majority of Spanish League fans today don't think that big teams like Madrid, Barcelona and Atletico Madrid are still unable to catch up with Girona, after the international break Girona will face Bilbao, Bilbao will definitely try to threaten Girona's position.
Girona is just two points ahead of Real Madrid, four ahead of Barcelona and ten points ahead of AthletiCo Madrid so it will take them to loose one match and they will be a step below other teams on the table, so they are still not very firm vet and can at any point be displaced on the table.
I still don't trust girona well enough to be able to maintain the top spot on the table after the international break, most of the players in other big teams who have been rested well enough will be in a better form and I'm sure their performance will be brilliant so Girona definitely needs to put in more effort to be able maintain their spot but Real Madrid will definitely be very tough on them whenever they eventually meet and they will be a test on their strength.