Answer 1
It's rather impolite but still something you would want to know ... basically it's a warning that says that you stepped in some [poop]. More correctly the escrement is is one's trowsers. The idiomatic meaning would be, "you are full of it".
Answer 2
It should me mentioned that the sentence is grammatically wrong and the meaning is actually unclear. Saying something like to someone who speaks German would simply make you look like a fool.
"Du hast Scheiße an der Hose" would be a rather rudely phrased warning that you do have excrements on your trousers, however they might have ended up there. I can't detect an idiomatic meaning.
"Du hast die Hosen voll" (lit. you have your pants full) is idiomatic and means that you are a coward. On a similar note "mach dir nicht ins Hemd" (lit. don't wet your shirt) means "don't be a coward" or "don't worry" and I could probably think of a few more, but let's stop here. ;-)
"hast" is old English for the verb "to have". So "hast not" means "does not have".
Your sister
Nicht mehr Hosen means literally No more pants. It would be used in a sentence like Ich werde nicht mehr Hosen tragen. In English this means I will no longer wear pants.
Today where is your
It means, "What does your family do?"
The grammantically correct form is Ich mache Deine Haare, which translates as I am doing your hair.
How old is your Auntie? Wie = How Alt = Old Ist = Is Deine = Your Tante = Auntie
Wie sieht deine Familie aus = What does your family look like
It means listen to your nose.
Ich liebe deine Füße.
"Herr, wir vertrauen auf deine Güte" means: Lord, we trust in your loving-kindness.
Du hast keine Ahnung = You have no idea.