The usage of possessive case in English What is correct: "he is a friend of John" or "he is a friend of John's"?

The poem without a title [I've just tried to create some poetry in English. It is my first experience. Looking forward to your feedback. :)] Let us not disturb flowers in their flower beds, We have unbroken sunshine over our heads, Sky is blue of the sunniest hue, Here is you - Stay with me just forever in the rendezvous. Wait a moment and give me a chance to believe. Wait a second, you see.. I don't want you to leave. Wait a minute, just relish this Midsummer eve - How magnificent! Breathlessly teach me to breathe. Flowers dropping off sleep'ly in their flower beds, We're bathing in moonlight with its silver shreds, Sky is stunningly blue, Here is you - Stay with me just forever in the rendezvous.

Storytime: The swallow (trying to put some C1 vocab into practise, I created such a kind of fiction) Scorching heat escaped the Navias Delta a couple of hours ago, bestowing unbroken sunshine and light wind as a gift for all dwellers of the Bald Banks. The sky was turning gold as the sunset was drawing nearer. A lonely cloud was sleeping in the lofty heavens, motionless in its most idle manner, for it had no aim to flow anywhere else. White butterflies were having the time of their evanescent lives on the sandy shore, soaking up the sunshine, field mice were restlessly running around, hiding cereals into their clandestine storage, a swallow was teaching her offspring how to fly high. The birds were surfing in the air up and down, demonstrating their maneuvers to the sleepy sun. Yet to waken was the cloud and it did not like the birds' jocund play. The only thing it ached for was to forget about the annoying air-divers. Grumbling in hatred it began to swell. The lethargic yellow round noticed the unexpected guest's endeavor, but was too weak to cease its growth. Suddenly, gale-force winds hit, whistling among the trees. It was the cloud which had summoned them. And being doomed to surrender, the winds called it 'the darkness', for it had covered the sky with a nebulous gloomy blanket. The swallow was crying and sobbing in order to alert her kin. In vain! As the winds were picking up, she had no chance to be heard - her chants were muffled by rumbles of thunder. She swooped low to the river, which had burst its banks, spread her wings and soared up into the blackness. It was pouring with driving rain. Although heavy drops were striking the bird, she had no determination, but to defeat the darkness in her last fight. Higher and higher, up to the very zenith, up to the very edge did she fly. Dashing through the cloud, she decided to look back at her shady haunt, catching a glimpse of the familiar trees and brooks to which she had become so attached. It was the last thing she saw, for she was soon covered with dense, suffocating fog. And then the endless clap of thunder blared out, and the blinding flash of lightning struck.

The leopard (a translation of the article from Student's Book (Round-up 6) Quite a lot of scientists consider the leopard the most advanced wild cat. They even call it the supercat. It is smaller than a lion and tiger, but more agile and quicker. The leopard is a perfect well-armed hunter. Its fangs and claws are as sharp as needles and as deadly as blades. This wild cat can run fast and smoothly, and carry its prey in his jaw heavier than the leopard itself. The leopard can run at the speed of about sixty miles per hour but it fails to beat the cheetah which is the fastest predator on Earth. The leopards living in the Amursky Krai have soft and thick winter fur. In summer it becomes shorter, rougher and thinner, but the pattern remains as bright as it was. If the leopard lives in warm countries, e.g. in Africa or Asia, its fur doesn't change throughout the seasons. There is the black leopard. Although people often call it the black panther, it is the same leopard, but with black fur. You can see the same spots as the leopard has, yet even under the bright light it won't be easy. Very rarely can you see the leopone in the zoo. This hybrid of the lion and the leopard keeps up the appearance of the lion, but has such brown spots on its coat as the leopard does. Leopones are smaller than lions, but bigger than leopards. Although the male leopone has a mane, it is not as thick as the lion's one.