Even if we don’t speak it most of us have been exposed to some Spanish here or there either learning some phrases or at least learning how to pronounce street names.
This applies to Brasilian portuguese.
Aside from a ton of words that are of course different I think the main reason that Portuguese speakers can understand Spanish speakers much more than the other way around is the pronunciation of the letters is often VASTLY different.
One of my daughter’s teachers is Mexican and we are learning Portuguese together. I wrote this list to her of basic pronunciation differences. Once you get an idea of that you’ll be able to guess how a word is spelled. At that point you’ll be able to realize what spanish phrase corresponds.
example “Donde” as in “Donde Esta,” which most of us non spanish speakers probably know anyway, in Portuguese sounds like “Ongee” but it’s spelled “Onde” which is just Donde without the leading D. “Onde EstÃ¡” Learning from scratch you’ll of course go with the pronunciatino guide that comes with your lessons but a little up front review of pronunciation might make it easier to figure things out.
So in general (pronunciation examples are english pronunciation not spanish):
D is typically pronounce like a G
Dia (day) sounds like Jia
R at the beginning of a word sounds like an H
Rio is pronouncd like heo
T (usually “Te”) is pronounced like Chee
Frente (front) is pronounced like Frenchie
M at the end of a word is pronounced like an N
Sem (without) Is pronounced Sen
L at the end of a word often sounds like a U
Brasil sounding like Braziu