@kim2116 I have a similar scenario as yours, for the days that I need to be at the office, I have a dogwalker come over around lunch to take my labrador for a walk. It's not very expensive, I pay around 10 EUR. But I saw cheaper and even free offers too.
I don't thinks it's OK to leave your dog alone for more than 6 hours consistently. If it happens a few times, ok... but it will definitly make your dog unhappy.
And as others have pointed out. Puppies are a lot of work the first 1-2 years, need constant attention. So I recommend getting a shelter dog, there are too many of them being put down and locked in cages.