When you buy a puppy your entire world is about to change. A pet is a member of the family, so imagine you just had a kid. Your schedule, your spare time, everything will have to be renegotiated in order to include the new member of the family.
But most of all, and especially at first, dogs require training. Do not assume dogs are smart enough to guess your every thought. Also, you cannot talk to them as you would to your neighbor. They need training and that’s about it.
Until at least four months old the dog will use any space as its personal toilet. First because he can’t help himself, and second because he doesn’t know any better. In order to reduce the amount of feces that you have to clean up you need to take him out for a walk at least every three hours. Which means your schedule must be really flexible to allow that. Yours or another member of your household’s.
Also, you must correctly guess your dog’s nature. Some dogs respond best to rewards. So when you take him out teach him to come to you every time you call him by rewarding him with something. Some dogs go for food, some for toys, some for playtime. Regardless which it is, you need to identify it and work with it. For example, a Retriever is extremely greedy and he will literally do anything for a bit of food, while an English Bulldog is more thick-headed and possessive and will more likely respond to a toy he just has to have.
You have to be patient. The entire point of the exercise is for you to get used to the dog’s characteristics and for him to get used to yours. It’s always a two-way deal, never just a one-way deal. If your dog is not overly aggressive, refrain from keeping him on the leash whenever possible. Dogs enjoy their liberty and it’s no need to limit it for no reason. teach him to walk beside you. You can achieve that through reward. Do not reward him every time. Do it randomly so he can never learn when he’s about to get a treat or not. In time, he will forget about the reward and will come to you out of habit. Also, do not call him too often as he will get bored and ignore you. Call him only when you need to, not just for your fancy.
The training takes months, sometimes years. Be patient and you will have a friend forever.