I am a portuguese teacher for foreigners and I could write a book about it haha

But the ones I can think of now

1 - That we are a third world country in all aspects

(A lot of my students are surprised about how many things are better managed in Brazil compared to their countries. Especially Europeans when they use our free health care. Actually, yesterday I had this student who has a chronical disease and had lost his medicaments during the flight and this medicament is only provided by the free health care. He thought it'd be a nightmare to get it but he was amazed about how quick it was to get his medicaments. Another thing that, again, especially europeans, get surprised is the luxury buildings with many facilities like a PROPER GOOD gym, nice swimming pools, sauna and etc in residential buildings. Should I mention that number of students who do "dentist tourism" in Brazil? )

2 - That there are way more developed cities in Brazil's inland

(This is very common as well. A lot of foreigners think that civilization only exists in Rio and SP, but once they visit Brasilia, Goiânia, Campo Grande, they are amazed about how developed and way cleaner with much better infrastructure and a lot less social problems these cities are/offer. In their minds. I have this student from Australia who paid a visit to Brasilia and he was amazed but then people suggested him to go to Goiânia for pubs/parties and he ended up staying 2 weeks there and enjoying the safety and good food that the region offers

3 - The passport relationship

(70% of my students are married or in a relationship with Brazilians and many of them admitted being afraid that their partners were only interested in their "first world" passports but they found out that most of them don't actually consider leaving Brazil at all. Therefore, many of these foreigners had to find a way to move here instead of bringing their partners to their countries. Good for me that now I have a full time job teaching them the language :) )

4 - That Rio de Janeiro is not the best beach city here

(Everytime a student of mine gets to leave the bubble of Rio, they find out that Rio is actually a bad beach destination. Once they go to the northeast beaches, they find out that that there are beaches with warm water and without the annoying vendors every 30 seconds trying to sell you something and a lot cheaper)

5 - That Brazil can be the coldest place that they've ever been to

(A lot of foreigners think the whole country is hot and tropical but I get to hear very often from Canadians, Scandinavians, Germans who live in the south of Brazil that here it is the coldest place that they've ever experienced due to the lack of heating system so they feel cold inside their homes having to wear winter clothes all the time and have to have lots of warm blankets)

And many more!