Men’s GUCCI 'Re-Web' sneakers

White/black Re-Web sneaker. These are a new Gucci size 8, I typically wear a size 9.5-10 US on sneakers. I purchased them in October 2024 in Florence Italy, however I have not wore them (see pictures). I selling them because my narrow feet cause the heel to slip when I walk. I tried using heel pads and foot inserts but nothing seems to work.