Please capitalize where necessary: feel its peacefulness. visualize the face of some inspiring person; feel you're in his presence.
A: Feel its peacefulness. Visualize the face of some inspiring person; feel you're in his presence.

Q: 1794: the u.s. military defeated the tribes of local indians at fallen timber.

A: 1794: The U.S. military defeated the tribes of local Indians at Fallen Timber.

Q: nitrogen is a basic element like oxygen.
A: Nitrogen is a basic element like oxygen.

Problem: if you receive a spam mail that is not detected, click on the spam blocker button, and the spam mail is removed from the rest of the 8,751,292 spamfighters in 238 countries/areas in seconds.
Can you repeat this sentence, but capitalize it?
Answer: If you receive a spam mail that is not detected, click on the Spam Blocker button, and the spam mail is removed from the rest of the 8,751,292 SPAMfighters in 238 countries/areas in seconds.

Text: you may not get what was wrong, but you can recover the files from the physical hard drive using recovery software.

Correct capitalization: You may not get what was wrong, but you can recover the files from the physical hard drive using recovery software.

Problem: internal surface of carbon steel tanks
Can you repeat this sentence, but capitalize it?
Answer:
Internal surface of carbon steel tanks