Ý´m practising compounds combined with genitiv and locativ.

Ýf somebody would like to correct me that will be great

Annesinin büyük evinin ön bahçesinindeyiz.

We are in the front yard of the big house of his mother.

Orhan´Ã½n erkek kardeþinin yeþil sýrt çantasýnýnda ne(dir)?

What´s in the green backpack of the brother of Orhan?

Senin evinin anahtarý mutfak dolabýmýn en yüksek çekmecesinda.

The key of your house is in the top drawer of my kitchen cupboard.

Kimin oturma odasýnýndasýnýz?

Whose sittingroom are you in? (plural)

would anybody like to correct me please...?

This is from one learner to another, so take this with a grain of salt. 

Annesinin büyük evinin ön bahçesinindeyiz.

I know tureng.com give ön bahçe as front yard, but I´m wondering if it wouldn´t sound better as:

Annesinin büyük evinin önündeki bahçedeyiz.

And also, for: Senin evinin anahtarý mutfak dolabýmýn en yüksek çekmecesinda. - I´m wondering if it shouldn´t be ev anahtarý instead of evinin anahtarý - the house doesn´t own the key, it´s the key to the house. Even in English I haven´t come across anybody saying the key of the house, it´s usually the house key or the key to the house.

As far as the suffixes I think all is correct.

Again, I´m a learner, so I could be wrong here. Maybe somebody more advanced or a native will double check.

Orhan´Ã½n erkek kardeþinin yeþil sýrt çantasýnýnda ne var?

... en yüksek çekmecesinda    => ..çekmecesinde : vowel harmony

...odasýnýndasýnýz? => odasýndasýnýz?