Tagalog: siya ay, yaon ay, ito ay etc.

What is the contraction for these words: 'y? I'm wondering what the shortened word is supposed to be. Also for sapagka't - what is the 't? (please tell me where did you get this)

I was supposed to write a whole entry in Tagalog and realized I am limited in my vocabulary so here goes a small attempt:

Ngayon kumain ako ng macaroni & cheese at lutong manok. Nag-aral ako para sa eksam. Natulog ako. At pumunta ako sa simbahan.

(Translation: I ate mac & cheese and cooked chicken today. I studied for an exam. I slept. And I went to church)

Obviously you can tell I'm not good with past tense, the infixes, prefixes, etc. Salamat for the corrections.