Как поставить это предложение в отрицательную форму there is a bookshelf by the window

There isn't a bookshelf by the window

1. The doctor gave the patient some practical advice. - Some practical advice were given to the patient by the doctor. 
2. She always gives medical help to her patient. - Medical help is always given to the patient by her. 
3. They opened a new hospital in this town last month. - A new hospital was opened in this town by them last month.
4. Many people know this doctor. - This doctor is known by many people.
5. They give children all the necessary medicines. - All the necessary medicines are given to children by them.

1. предложения в времени.
Все предложения в времени.
2. предложения в passive voiсe.
The man who was thought to be the discoverer of America was born in 1451 in Italy.
3. предложения с глаголом to be.
The man who was thought to be the discoverer of America was born in 1451 in Italy. His name was Chris­topher Columbus. At that time the life of a sailor was full of adventure and danger, so Columbus had many exciting experienc­es. Knowing that the earth was round, he decided to reach India by sailing to the west. It was very difficult for him to organise his expedition as nobody wanted to help him.