çok çok teşekkürler

Önce, herkese çok teşekkür ederim. Memnuniyetle iyi Türkçe konuşmak istiyorum. Çok şükür bana yardım edeceksiniz. Ben de size yardım edeceğim, belki.

Ama, sorum var. And I´ll switch to English since the initial question was also put in English...

Why doesn´t "istemek" want the 4th case? I mean, you always want SOMETHING, right, so shouldn´t this something be in the 4th case / accusative case?

Teşekkürler!

Yes actually you are right. If it is direct object of a transitive verb it is accusative. But there are accusative suffixes in Turkish which make a noun direct object of a transitive verb. They are -ı, -i, -u, -ü. Some nouns doesnt become direct objects of some verbs without using them. That is why I said verb wants object to be accusative. I guess I should have said verb wants noun to have accusative suffix to become a direct object. I will not do this mistake again. 

But it does.

istemek
1. /ı/ to want, desire, wish.
2. /dan, ı/ to ask (someone) for (something).
3. /ı/ to ask to see or talk to (someone).
4. to be necessary; to require.
5. /ı/ to ask for (a woman) in marriage.

The definite object takes ACC when accompanied with istemek.

                              Bu gömleği istiyor musun?

                              Benim onu satın almamı istiyor musun?

The simplest istemek construction where the subject of both istemek and the other verb is one and the same can be (and usually is) built with simple MEK infinitive.

                               Her sabah pazara gitmek istiyorum.

bilmek BTW behaves the same way. They are the only two exceptions to the rule but they occur very frequently of course so it is necessary to know this.

So... because konuşmak is a verb it doesn´t need the 4th case? Teşekkürler!

Being definite or not if a noun is a direct object it is accusative. But some verbs want nouns to be definite with taking an accusative suffix. For example "öğrenmek" always wants its object to be definite. But "istemek" sometimes wants it to be definite and sometimes not.

Simply:

1. If an object is direct object of an transitive verb it is accusative. (With or without accusative suffix)

2. Some nouns dont be direct objects of some verbs without accusative suffixes (-ı,-i,-u,-ü ).

3. If a noun has an accusative suffix it becomes a definite direct object. 

Aramıza hoşgeldin! Her konuda sana yardımcı olmaya hazırız  

arkadaşlar çoğu zaman yabancı müzikler dinliyorum yerli müzikle pek aram yoktur
şarkıların türkçe sözlerini merak ediyorum nette bulamıyorum
hani arada bir bana yardımcı olurmusunuz ? 

Buradan bakabilirsin : http://www.cevirim.com/