Hello, I would like to suggest these corrections:
Tristezas longas de mim.... adj. longo/longa means "long", so it is to be "my long sadness" (if you want to keep the plural, maybe "sorrows")
Silêncios interrompidos Por saudades que não sei ............ Silences interrupted by longings that I don't know
Porquê sonhar sem dormir ... Why dream without sleeping (there is the word "porque - because", and the word "porquê - why", they only differ in the pronounciation of the last vowel)