Change it to what? You say that Portugese is not offered, so what language do you want? English?
The language of the app is determined by the system language, but if the system language is a language that is not supported in the app, then it may choose a random other language. Try this: set your system language to English. Start Photoshop. The Photoshop language should now be English. Change your system language back to Portugese. The Photoshop app should now stick to English because it does not support Portugese.