I have just got a new pup. She is an American bulldog. Cute as. Long time since I had a pup.
How much do I feed her and how often. She is 8 weeks old. Weighs 5 kg and.

What has puppy been eating before you got her? Wet or dry food? You need to find out what sort of food she was eating so as not to upset her delicate system. Get the same food for now so she can at least eat something familiar before you go out and change her diet. You need to feed a puppy that young at least 3 times a day. Be sure to take her outside right after eating so she can get used to going outside also.

You should feed 3 times a day until 3 months old, and at 6 months you can cut back to once a day. Most puppies come from the breeder too fat. Your dog definitely should be narrower at the waist than the hips and chest.
You should be able to easily feel the ribs, but not see them. Each dog is
Different. Standard recommendations are a good place to start, but each dog
Must have its food adjusted to its individual needs. Here is a link to a good illustrated guide,
http://www.longliveyourdog.com/twoplus/RateYourDog.aspx

A half cup would be a good starting point.

For more info, see the sticky at https://www.askmehelpdesk.com/dogs/information-articles-our-dogs-expert-labman-53153.html#post251802

Most dog food bags will have a weight chart and the feeding frequences. If you still need more advice talk to a licensed veternarian. I am afraid I do not know of a licensed vet on our sites.