Months, nationalities and languages are not capitalized.
- Sou brasileiro e comecei a estudar inglês em janeiro.
Excellent example! I'm a Brazilian and I began to study English in January. (Actually I'm an American and I forget when I began to study Portuguese ;) )
Na verdade, sou americana e esqueço quando eu começar a estudar o português
"Na verdade, sou americana e esqueço quando eu comecei a estudar (o) português."
"Na verdade, sou americana e esqueci quando eu comecei a estudar (o) português."
duolingo doesn't support the UK version. We have semesters at university, terms otherwise.
In my US experience, trimester almost always refers exclusively to periods of pregnancy.
I have also only used this in reference to gravidez, and I'm a native speaker.
I am American and I only use semesters for referring to university periods. Trimester might work for businesses too, but the term quarter is definitely more common.
Semester vs Trimester depends on the university in the US. This sentence seems normal to me.