Sorry if i missed tutorial and asking so simple thing but i couldnt find anyway to retrieve my items back on listing…
Hello. There’s an easy way for that. You first need to click on the listed item you want to retrieve.
Then, you must click on the “edit” orange button.
After you do so, scroll down a little till you see the “return item” button and click on it as well.
Then, it will pop up a window with an orange button that says “Start bot trade”. Click on it and that will make the bot starts a trade offer sending you your skin back to your steam account.
And to finish, you can now click on the “See trade offer” button so it will open a window to the trade offer for you to confirm it. After confirming it, go back to the same gameflip page and click on “i’ve completed bot trade” and that’s it!
Hope that helps you 
Good illustration - It seems obvious unless you don’t edit the listing once posted.