1.Is it halal to eat the meat (like chicken, cow , goath, etc and products that contain these meats) from non-muslim supermarkets slaughtered in a non-islamic way (without basmala) ?
Meat that has not been slaughtered islamically cannot be eaten, even in small amounts. To do so is an enormous sin. Saying bismillaah does not not change this.
2.Is it halal to eat fish from those supermarkets?
Yes, fish is allowed to eat, even if caught by a kafir, because it does not require slaughtering.