I know using 'i' character in lower case is wrong, specially when I'm talking about my self, for example : i went to gym yesterday. how about 'is' letter? can I start my question with lowercase 'i' like is she Portuguese?
All sentences, questions and statements start with a capital letter.
Is she Portuguese?
Are they Portuguese
If the word is not the first letter of a sentence it doesn't have a capital. The word "Portuguese" is capitalised because it is an adjective made from a proper noun "Portugal"
When is she arriving?