I was really concentrated.
I had switched off the TV and the radio... ('telly'? nie mam tego słowa w słowniku;>)
I was writing ... I heard...
I went to check what was that...
when I was doing my homework
everybody(jak już wiecie;>)
when my mobile phone started ringing. It turned out that my parents were phoning me to say that they had forgotten to ...
would come(poza tym nie za bardzo pasuje mi jeszcze jedno zdanie, może jest dobrze, ale na Twoim miejscu lepiej napisałabym At once I had decided to find out what has happend when...)
/sorry za ewentualne mistakes;>/