Breeding

Question
Hello, I have a male Great Dane and a female great dane.
both danes are from completely different litters and areas in California.
My female is 11 months old and in heat. my male is 8 months old.
Zeus (the male) keeps trying to mate with Herra (the female).
I try my best to keep them away from eachother. But herra cant be in the crate all day, and neither can Zeus.
I'm worried that she might get pregnant.
we do want to breed, but not just yet.
I know she needs to be older.
when do you think i should let them mate?
he birthday is on February 10th, and Zeus is on May 8th.

Answer
I do not typically answer questions pertaining to breeding. I will only answer the basic questions but I first have some questions for you.

What color is your female? What color is your male?
What health testing did the parents of your dogs have and what were their results?
What is the purpose for you breeding them?
What health testing are you planning to do?
What experience do you have with breeding, whelping and raising a litter of puppies?
How do you plan to find homes for your puppies?
What are your stipulations for the homes?
Will the puppies be listed on spay and neuter contracts?
Will they puppies be sold on full or limited registration?
What kind of guarantee will you provide for your puppies?
What will the stipulations of your contract be?
Will you be willing and able to take back ANY puppy and ANY time in their life if the owners can no longer care for the puppy they bought from you?

Dogs, whether they are a bitch or dog should NEVER be bred until after they are 2 year old both male and female and have been cleared through APPROVED health testing methods, and no not just a vet visit where your regular vet tells you they are "healthy"