English always needs a verb. So it would have to be "Your clothes are mine."
That said, the sentences have different meanings.
"Your clothes are mine." means that the clothes had been yours, but they are no longer yours, they are mine now.
"I have your clothes." means that the clothes still belong to you, but I have them because I borrowed them, or you left them in my car or something.
sana_saleem, in "senin giysilerin bende" i can say that "bende" act as the verb of the sentence: "bende"= "is at me". Do you remember all the sentence of this type in the locative skill? As: "cay onlarda"="we have the tee", "elmalar sende"="you have the apples", "ördekler bizde"="we have the ducks"......
The -in in giysilerin is not genitive; it's the second person singular possessive suffix.
After a consonant, it happens to look identical to the genitive suffix, but formally, the genitive suffix is -İn (which takes a buffer consonant -n- after vowels) and the second person singular possessive suffix is -n (which takes a buffer vowel -İ- after consonants).
(The capital letter here indicates that the actual vowel depends on vowel harmony.)
If we take a word ending in a vowel such as elma "apple" or kedi "cat", you have elmanın, kedinin for genitive but elman, kedin for "your apple, your cat".
But after a consonant, as with kitap "book" or baykuş "owl", the two look identical: kitabın, baykuşun.
Similarly with the third person singular possessive suffix and the accusative case ending, which look identical after consonants as -İ (e.g. kitabı "book (acc.) / his/her/its book") but distinct after vowels (e.g. elmayı "apple (acc.)" but elması "his/her/its apple").
As for -de, that's the regular locative suffix, and is used here to express that "your clothes are at me".
At least in this course, this is how possession of a definite item (YOUR clothes, THE elephant, THAT book) is expressed -- by saying that it is "at me, at you, at Selcen" etc.
Possession of an indefinite item (AN elephant, (SOME) clothes) is with the "my/your/Selcen's ... exists" construction, e.g. elman var "your apple exists = you have an apple".