Open "contacts", the full list of your contacts would be there. www.italki.com/contacts/partner

I know, but on my profile there aren't shown all my friends. So How can I remove those that are not shown?

maybe u can tell them ur Skype or WhatsApp or line or Instagram...just chat with them in other communication softwares.

Go to your profile and put the mouse on your friend's pic, there are three options, remove friend, send a message and give a gift card.