Kalbimi satiyorum.

İm selling my heart.

thank you zeytinne.

 kalbimi=my heart

satıyorum=satmak=to sell

 What is the i at the end of the word for?

Kalbim= my heart

satıyorum= I am selling

Kalbim(i)?

i is accusative case

Is it because it´s the object of the verb satmak which takes i/ı ?

thank you both

For example if you say "elmas satıyorum", you mean "you sell diamonds" (any diamond)

If you say "elması satıyorum", you mean you are selling THE diamon (a specific one)

Thus, when you refer to something that belongs to you which is unique (like your heart), you have to use the "-i" case