My sSunday day

"Sunday" or any other day of the week would be redundant to say alongside "day"
Titles have special capitalization rules

Today is sSunday in Brazil, and it's rainning (right now).

Days of the week are capitalized.

You might say "it's raining /now/" when it is important to highlight that it just recently started to rain, which isn't important for your particular sentence. An example where you might say this: "I was going to work in my garden, but it's raining now, so I'll do it tomorrow." This means it's raining and it just began recently.

Otherwise, you might say "right now" if you still want to insist that it is raining at this current moment.

I'm studying two languages at the moment, English and German.

I think what is so difficult, especially for German, because isis that they are so different ofrom my native language, and sometimes I confuse with somesome German with English words, because they are similars.

Edited for clarity

That's it's for today.

Tomorrow I will have more.