Could you please correct it?

We often hear sentences/maxims* such as "Happiness is not the absence of problems, but the ability to deal with them." Everyone wants to avoid getting into trouble, while the best advice is to learn how to address it. Being surrounded by difficulties can be annoying, but only if you are unable to handle them and happiness is one of the key points.**
Admittedly, no one can deny that he or she has to face various problems at times, however, each situation can turn out differently***. Some have an extremely difficult time in overcoming them, some can even hardly solve them, while others are able to make good use of them; not only handling them successfully, but taking a lesson to avoid larger losses****. The secret behind it is to be positive. From my daily experience and observation, since you have to face those difficulties whatever, why not be delightful***** and strong enough to defeat them easily.
To sum up, in order to develop a problem-solving ability, we could view the problem as a way to challenge ourselves and imagine the bright tomorrow when we overcome it, and the most important, devote ourselves wholeheartedly to it.

Notes:

*can you think of a word to describe this kind of sentence?

**key points to what?

***(... depending on the way one deals with it.)

**** you cannot make "huge" into a comparative, but "huge" is so massive.

*****"delightful" doesn't really fit here, maybe "cheerful"?

About my little one, Nila

Nila, my love, my little girl, is studying in KG. Nila came into our lives 5 years ago. She always sits in between us, as she is very possessive. It is a very tough job for me to give her food. Most of the time I have to sit for an hour at a time to make her tummy full. She was very skelt(?*) earlier, but now seems to be better than before.

*"Skelt" is not really a word in English. I imagine by the context, that you mean "thin" or a related synonym - http://www.thesaurus.com/browse/thin?s=t

Describe your house

I live in a flat. It's not big, but very cozy. I have my own room with a bed, bookshelves, a table and a wardrobe.
The room doesn't look that "hygge", however I'm trying to make it more and more comfortable every day.
I have a cactus and an orchid,  and a funny "ice cream" container for pens and toys. Yep, I adore some of my old toys and they still live with me on the bed. These small things bring harmony to the flat.
And last but not least, there are my books. I mostly like language books: dictionaries, self-instruction tutorials, literature in English, French and Spanish.
It's a kind of magic to look at bookshelves and to know that you have read nearly all of the books.
I love my flat and, as Mary Kondo suggests, I thank it for welcoming me (*) and for being my home.

*for the welcoming feeling it gives me

What ways do recruiters use to look for potential candidates ?

In the 2000s, to fill empty positions, recruiters tended to advertise their recruitment programs. At that time, TV was also a way to announce job hunting news. Each time they posted their programs, companies had to pay a quite high cost to let their information make impression on candidates. After that, job hunters went to companies to meet recruiters directly. If you lived far away from the company and you wanted to apply, you could send your CV by post, but (*) you had to take 5 or 6 days, or maybe even one week for a response. It was quite a long time and you couldn't be sure whether the human resource department had received it or not.
Over the last few years, due to the development of Internet, looking for jobs has been not as difficult and complicated as before. You just need to become a member of job hunting websites, and recruiters can update jobs and their information to attract potential candidates. That is also a good way for job hunters, as they just need to send their CV to the websites, wait a few moments, and recruiters will receive it.
Yet, for some organisations, using the Internet is just the way to inform the public, and applying in person is still a priority.
Since graduating from university, I've sent my CV to many companies, but just a few companies have responded. This makes me think that my request was either lost or ignored. Although, applying for a job(**) directly takes longer and has a little bit of disadvantage, at least you can be sure that your application letters are sent into the hands of recruiters.

* It is not "proper" written English to start a sentence with "but" -- "However" or "Yet" would be better.

** "to apply or a job", but "to send a CV"

Part1 Please help me correct my writing, i really appreciate your comments.

I'm writing about how important every finger is to me. Of course, we usually use our index fingers and thumbs more than other fingers. But after I got an injury, I found my little pinky finger to be much more important to me.

The thing is, I've been working out regularly, cos I wanna keep fit and healthy for the sake of myself and others. I don't wanna be a burden to anyone when I'm older. And I wanna keep on donating my blood for those who need it. So, I've been doing cardio and body weight workouts regularly.

One day, I did some push-ups quite aggressively without proper warming up, cooling down and stretching. I just forgot. So, my negligence caused me to get injured. The next day, about 5 am in the morning, I woke up cos I felt a complete numbness in my left arm and hand. At that moment I thought that I might have slept on my left arm. I just turned to the other side and thought that the numbness would be gone, but it wasn't. 2 hours after that I got up and outta the bed and then I knew that something wrong had happened to me. I waited for 5 hours after I felt the numbness, cos I thought it might gradually recover. However, when it didn't, I decided to call the hospital to make an appointment with the neurologist. I got to see him that morning. The doctor examined and tested the movement of my arms and hands. It turned out my left arm was not weak at all. The weakness of muscles is the most concerned (common?) issue for the doctor when it comes to numbness. Well, my left hand could grip as hard as the right one. The area of the numbness was from the tips of my left pinky and half of ring fingers, through the palm and under those fingers to the wrist. That led to the conclusion that I had an ulnar nerve entrapment. Somehow and somewhere the nerve was trapped. And the most common area of entrapment is the elbow. But it can be found trapped in the wrist also.

* Be careful using "spoken" expressions: e.g, cos, outta, wanna, gotta etc in writing.

Are you a strict person of flexible person?

I am a flexible person. I have learned how to work with people and how to live with people from the many teamwork experiences during my time at university. I think flexibility is very important when it comes to working with many people. My team members call me "cocker spaniel" because of my rounded character and outgoing personality.

Is he a spy or not? :-)

I have a colleague... let me give him a nickname, hmm, for example - Nick. He is a few years older than me.
Where we work no one knows anything about him, except that his mother is Russian (I saw his ID card, so I believe this to be true) and he does (for emphasis)speak Russian very well. He says he has a brother and a sister, but no one has ever seen nor heard them, so we don't know if this is true or not. And that's not all. No one knows where he lives, whether he has a girlfriend/wife and children or not, or even whether he has a pet.

Sometimes I ask him to give me some chocolate. He always has some and I always get some from him, but all of these different chocolates have Russian label. Why?

Another interesting thing: he goes  abroad many times -- to Austria, Slovakia, Turkey, America and so on. However, the interesting thing is that he goes everywhere by airplane (also to Slovakia and Austria, even though they are in our neighborhood (close enough to drive to)...). When he gives us his plane's departure time it is always the same as a plane which is going to Moscow. And when he comes back, it is always the same as a plane which arrives from Moscow. Is it a coincidence... or not? :-)

My first topic

Hello!
Could you check my topic, please!
Yesterday I went to the grocery store. I normally buy bread, milk, eggs and cheese, but yesterday I went looking for some cheese in the cheese aisle, but I couldn't  find the cheese that I prefer. I asked the shelf stacker/staff: Where can I find X brand of cheese? The member of staff answered me: Oh, I'm sorry! We no longer stock this cheese, because their parent company had quality control issues. I said: I guess I'll just have to try a new brand. I bought all the products I needed, except cheese. I didn't choose a new cheese brand, but I didn't leave the store empty-handed, either.