problem in product quantity

Hallo mr/mrs,
please i have problem in product quantity:(i did it Available in cart and checkout but i cannot modify the product quantity so as increase or decrease the quantity for the product ,whether on the product page ,on the cart or on the checkout page).Also featured and Best seller for products is like some of them. the last problem is that the counter for the shopping cart or for the wishlist become empty on the home page ,meaning i cannot go back to see the products i added.Aso how can i put the color for any product as default (i mean if i donnot choose the color i see the message for adding but i want to make any color as default without see this message).
Note: all problemes you can see it in the video that i sent it with this message
please i wait your reply and thank you .
Ebrahim bari