A couple of considerations
My parents are lucky they have a farm.
While that is a great advantage for the quality of life of the dog... it is
not a substitute for guided exercise and stimulation. As everybody has said, these working dogs are highly intelligent and energetic. If you do not manage their mental and physical energy when they are young, they will likely develop delinquent behaviour. As
@LostHighway said; destructive or neurotic behaviors are real risks.
So while the farm is a great 'backyard'... you will still need to enrich the dogs experience by playing/walking with them daily. This gives the dog something meaningful to do
and is a part of forming a bond and establishing good behaviour.
Again it is worth emphasising; the reward of bringing an intelligent animal into the family is high - but the amount of attention and effort that requires is higher than other breeds.
I think at the end it will be my dog
The main advantage that we have is that i'm with them i work in their farm in summer. So when the dog will arrive in end january i will be there (even if i'm working in a restaurant in winter) . That's why i said that it will be my dog at the end.
Think carefully about the training dynamic here. You might want to have a family meeting about that. Life will be easier for everybody if you all adopt the same approach to training and socialisation. Ideally you and your parents want be incentivising good behaviour and managing bad behaviour in the same way.
It is also best if you are a regular feature of the dog's life in the beginning. As obedient as these dogs can be, if trained well, that is a function of the relationship they share with their trainer/family. If they are distracted by something interesting, they are not going to listen to a stranger.
They have a cat. A fourteen years old cat
It sounds like the wheels are in motion already. The welfare of the cat is a completely separate issue...
I don't mean to be cruel... but the cat is likely to experience a decline in welfare. Fourteen years old is pretty senior for a cat. For a lone cat that is used to free reign and undivided family attention, unless you have a particularly sassy or chilled out cat, it will likely be miffed by the dog. It is unreasonable to expect a cat to have any interest in getting along with a dog they did not grow up with.
I highly, highly recommend you read tips how to introduce them.
Again, taking your training seriously will help. Similarly, adjusting the family dynamic and territory. Consider how the cat can have a safe space - maybe part of the house that the dog cant access. If the cat is very cuddly, make extra effort to give the cat cuddles - don't let that get distracted by the puppy. If the cat has a routine, try not to break it. Be very strategic and careful about introducing the animals. Manage introductions incrementally. Both in terms of proximity and time spent together. If you are having success, think about ways to make the older cat higher on the pecking order (e.g. feeding first etc...)
If you are lucky the cat and dog will eventually get along. A more likely good outcome will be an uneasy long term truce - the cat may have no interest in interacting with the puppy but be happy in their own safe space.