The culture here is to never raise your voice or get mad in public

This stereotype also exists about Cambodia, the country I've lived in for 4 years now. I can tell you that it isn't true about either Cambodia or Vietnam, since I've seen plenty of people in both countries get mad and raise their voices in public. The same happens of course back where I'm from in the US, and if I had to guess it happens at about the same frequency but I wouldn't rely on faulty human memory to make that judgment.

Viet are shy and have poor personal communication

This is just a ridiculous thing to say if you've never spoken to these people in their native language. I have actually gone through the arduous process of learning the language in Cambodia, and I can assure you that speaking in a foreign language clumsily and constantly being worried about your inability to express yourself will make you more shy than you are in your native language. And I have to mention that famous park in Saigon where foreigners are literally swarmed by Vietnamese people eager to practice their English... is that shyness? I never talked to so many strangers in my life as the couple of nights that I sat out there.

And actually, please do not think I'm vilifying you or calling you a racist or anything. I can tell from your post that you're a nice person, whereas in both Cambodia and Vietnam there are an outsized number of expats who are just straight-up mean, bitter, and racist. These people unfortunately end up influencing the perceptions that new expats have.

I'm only encouraging you to come in with more of a blank slate, and to not delude yourself into thinking that you can know anything about the culture after 1.5 months. I'll be more willing to hear out generalizations after you've been there for years, learned the language, and traveled all around the country. Have you even been outside Saigon yet? I've been to Saigon, and it's not representative of the rest of Vietnam.