Please capitalize where necessary: start playing and learning right away!
A: Start playing and learning right away!

Please capitalize where necessary: the natives declared that dorantes and later cabeza de vaca were highly effective medicine men.
A: The natives declared that Dorantes and later Cabeza de Vaca were highly effective medicine men.

Please capitalize where necessary: but the bride sat still, and said nothing, till at last the bridegroom said to her, “now, sweetheart, do you know no story? tell us something.”
A: But the bride sat still, and said nothing, till at last the bridegroom said to her, “Now, sweetheart, do you know no story? Tell us something.”

Please capitalize where necessary: acute stress is actually a condition of "combat readiness"; this mechanism was a very appropriate arrangement until the lifestyle of modern man became popular.
A:
Acute stress is actually a condition of "combat readiness"; this mechanism was a very appropriate arrangement until the lifestyle of modern man became popular.