Dear Thalia,In answer to your question about Contractions in English.
"Who �re", "What �re"; "Why �re"; Where �re"; "When �re"; Which �re"; "How �re"; are all used in conversation in the UK. They are also used in informal writing.
"My favourite subjects �re English and Portuguese", is pefectly acceptable to me, in spoken English, and in informal writing.
"My name �s Thalia/Maria/Les/etc". is used daily in speech and is frequently seen in informal writing.
I quote "A Comprehensive Grammar of the English Language" page 26, by Professor Quirk and 4 other English Professors.
"Contractions such as "didn �t" are appropriate in both informal and *neutral English; they are excluded from formal English".
*"Neutral English", is "normal English", midway between "informal" and "formal".
I quote "An A - Z of English Grammar and Usage", page 101, by Geoffrey Leech, Benita Cruikshank and Roz Ivanič
"Contractions are used in speech and informal writing. Do not use them in formal writing, for example, business letters".
I quote "Practical English Usage", page 132, by Michael Swann of Oxford University Press.
"Contractions are common and correct in informal writing: they represent the pronunciation of informal speech. They are not generally used in formal style".
A Private Note; Personal Letter; Scribbled Instructions; Diary; Shopping List; Novel; Book of Fiction; Written Conversation; Comic Writing; Personal E-Mail; Light-Hearted Essay; Popular Newspaper; Popular Magazine; are all examples of Informal Writing.
A Business Letter; Thesis; College/University Assignment; Essay on a Serious Subject; Serious Newspaper; Technical Magazine; Scientific Paper; Formal Written Debate; Non-Fiction Book; Official Proclamation; Notice; Written Record of Court Proceedings; Minutes of a Meeting; Business E-Mail; Job Application; Curriculum Vitae; are all examples of Formal Writing.
If you are in doubt, treat the subject as Formal, then you won�t cause offence.
I hope that this helps you.
Les