The horse

Horses are the best friends of  mankind . (Better to say: horses are mankind's best friend) A horse is very faithful and strong. In the olden days they were used to carry people and goods from place to place.Nowadays we use them in racing and in circuses. We call the male horse a stallion and  the female a mare.  and for the baby male horse (colt)and for the baby female horse(foal). Baby make horses are called colts and the females, mares. Personally, I like Arabian horses. so much. ("so much" has a childish or endearing mood. To sound better, you would say, "Personally, I like Arabian horses the most or a lot."

The horse

The horse is the best friend of mankind. It's very faithful and strong. In olden days* it was used to carry people and goods from place to place. Nowadays we use it in racing and circuses**. We call the male horse a stallion, and the female a mare, and for the baby male horse is called a colt and for the baby female horse, a foal. Personally I*** like Arabian horses so much.

* Or you could say "In the past"

** Racing is a sport,so is singular. A circus is a noun. Horses are used in a lot of circuses, so you would use the plural form.

*** I, when referring to yourself, is always capital letter

I hope this is helpful!