Is the donor obligated to fulfill the entire amount he pledged if he announced it publicly, and is it permissible for him to drop part or half of this donation?

Donations to charitable and permissible projects must be fulfilled, as Allah Almighty says: (And fulfill the covenant; indeed, the covenant will be questioned), and the Prophet, peace and blessings be upon him, said: "The one who takes back his gift is like a dog that returns to its vomit." Nothing of the donation is waived except in case of incapacity. One should pledge what they are able to fulfill, and ensure that the project being donated to (such as a cultural and sports complex) is free from Sharia prohibitions, for a person will be questioned about their wealth and how they spent it.