Давайте рассмотрим, как правильно использовать инфинитив в предложениях, которые вы предоставили. Мы будем заполнять пропуски нужной формой инфинитива. Вот шаги, которые нужно выполнить:

1. Первое предложение: "The man seems (to wait) for you. He seems (to wait) for a long time." Здесь оба пропуска заполняются одинаково. Правильный ответ: "The man seems to be waiting for you. He seems to have been waiting for a long time."
2. Второе предложение: "Perhaps it will upset him (to tell the news)." Здесь мы используем инфинитив: "Perhaps it will upset him to tell the news."
3. Третье предложение: "The key was believed (to lose) until I happened (to find) it." Здесь мы используем: "The key was believed to have been lost until I happened to find it."
4. Четвертое предложение: "The girl seems (to know) English very well. She is said (to spend) a few years in the USA." Здесь правильные формы: "The girl seems to know English very well. She is said to have spent a few years in the USA."
5. Пятое предложение: "I believe she deserves (to tell) the truth." Заполняем пропуск: "I believe she deserves to be told the truth."
6. Шестое предложение: "They seem (to discuss) something very loudly." Здесь правильный ответ: "They seem to be discussing something very loudly."
7. Седьмое предложение: "The house is known (to build) in the 18th century." Здесь используется: "The house is known to have been built in the 18th century."
8. Восьмое предложение: "She is glad (to see) that film. It has made a great impression on her." Здесь правильный ответ: "She is glad to have seen that film. It has made a great impression on her."

Таким образом, мы заполнили все пропуски в предложениях нужными формами инфинитива. Надеюсь, это поможет вам лучше понять использование инфинитивов в английском языке!