We own a house that dates from around 1870. A garage was dug in the 1960s at the cellar level. Metal beams were laid to reinforce the floor of the ground floor. Since 7-8 years the floor of the 1st floor leans more and more. 20 cm by 8 m! Is it possible that the beams between the ground floor and the floor are off? You can not see anything from the ceiling of the ground floor, but there must be at least 20cm between the ceiling and the floor of the floor. Is there a danger of collapse of the floor of the floor?
What you describe here seems very disturbing to me. It is high time to call on a building professional who will be able to judge the dangerousness of the phenomenon and diagnose its origin.
If it is as I thought I understand, the floor of the first floor that leans, it will scrupulously check the structure and perform as soon as possible: it is your safety and that of your family.
This may interest you