I see that turkish learners have a lot of problem with the words ending with the letters "p,ç,t,k".

In the rule, it says that if you have a word ending with one of these letters, and if you want to add a suffix that starts with a vowel,  they softens to "b,c,d and ð" respectively.

However, there´re many words that do not respect this rule.  In our lessons, we  give as exception just "one  syllable words". In one syllable words, the letter do not change.

There´re other exceptions, and I´m giving them now.

2. In some one syllable words, softening takes place.

Forexample:

Kap-ýn...kabýn

3. In proper names, softening never happens.

Örnek: Ürgüp´ e, Zeynep´in

4. The rule does not apply to words borrowed from other languages (this one is the most confusing)
Examples: Devlet-imiz, Tank-ýn, Hukuk-un, Hürriyet-imiz, Sanat-ýn, Millet-in, Bisiklet-in, Saat-in, Bilet-in

words´ origin is a must.....

Exactly, there are some exceptions that don´t respect the consonant harmony, these words (most of them, and not all of them) are derived from other languages, such English, French ...( but not Arabic)

Ex:

kamyonet => kamyoneti (it´s still ´t´ and it´s not kamyonedi, it´s origin is from french : camionette = small truck )

By reading, discovering the Turkish language, you can find most of those used words.

Bye

This rule maybe what the book says, but in practice (in speech especially), everyone changes the last k in this instance to the soft g. Thanks.