My boxer had 6 puppies... one of the puppies had a bad cleft palate hare lip.. so we had to put her to sleep.. And she has another puppy that has a hare lip but can eat and do everything else like the other 4. Will this be a big problem to the puppy when he gets bigger.. And has anyone had a puppy that had a hare lip and surgery fix the lip

Many questions here get a prompt, reliable answer from an appropriately trained and experienced member. I certainly have great confidence in my answers on things such as housebreaking. However much of my training and experience is about avoiding problems rather than coping with them. We have some other good regulars that might be more help than I am, but haven't heard from them for a day or 2. I dug up a question on the closely related problem of cleft palate.
We didn't do that well on it either although the links might help. You might be able to PM the original poster too.
https://www.askmehelpdesk.com/dogs/feeding-new-born-pup-36058.html?highlight=cleft+dog

You could do your own search too, at least that way you would know to evaluate what you found. Check American Veterinary Medical Association (http://www.avma.org). I trust them and American Kennel Club - akc.org (http://www.akc.org) more than many other sites. The AKC site should have boxer related links. I am appalled at how many sites have bad information.

I would urge you to do some checking before breeding your dog again. I don't know if hair lip problems tend to repeat or not. The owner of the stud needs to be told, and check also. It may be important to sell the littermates under spay/neuter contracts.