Two suggestions: 1. add a comma after "the Bulgarian Horrors" to make clear that it's a parenthetical comment, and 2. change the last part to "...in Serbia declaring war on the Ottoman Empire." Other than that, it looks really good.

I think it would be more common to use "suits" in this case, so "This hat really suits you". I would expect to see 'match' used when you're saying that one thing is similar another, e.g. "This hat matches your shoes".

It means that the other person is ignoring the problem. There's an idiom about "putting your head in the sand", based on the idea that ostriches do that (though, of course, they don't -- they wouldn't be able to breathe). Adding the 'everything's okay' just emphasizes that -- the person being spoken to is ignoring problems and pretending everything's fine.

Working as a children`s doctor in Norway

I am a paediatrician. I have been working and living in Norway for 12 years.
I work at the children’s department of the Førde general hospital. It has 2500 employees and serves as a central hospital for the county Sogn og Fjordane.
When I work the normal shift on the ward, I am in charge of the children from zero to 1 years of age, including premature babies.
At the outpatient department, I handle patients of every age between zero and 16 or 18 years.
I handle patients who suffer from asthma, allergies, cancer, chronic fatigue syndrome, developmental dysplasia of the hips, cardiac problems, hypertension, kidney diseases and more.

My job involves working 24-hour shifts on the ward. Then I am responsible for all patients between zero and 16 years of age. I deal with patients who suffer from infections (pneumonia, urinary tract infection, bronchiolitis), diabetes, premature babies, seizures and more.

[I'm hard pushed to see anything wrong with this passage, Annette! Perhaps the only suggestion I'd make (and it's not a very strong one) is that it might sound 'better' to say "...from birth to 1 years" rather than using "zero years", but that is probably just a matter of personal taste'

Hobbies

Travel to the USA

Traveling is one of my favorite hobbies. I love visiting friends and family, seeing historical sites, and experiencing new cultures. I would like to travel to the US to see the country with my own eyes. As I plan to study in the USA, I would like to get some experience beforehand.

What to do during my trip to the USA

I would like to see the university campus and meet some students. I would like to get to know their experiences and everyday life. Moreover I would like to improve my English and buy some books on American culture. I want to eat a real hamburger and explore the food culture of the US.

Interest (nature)

I love nature. I often walk in the nearby Sanglim park in all seasons. I like visiting cities, but I am very happy to stay in the countryside. My favorite seasons are fall and spring, because they are very colorful and full of change. Flowers are blooming in spring and the leaves change its their colors in fall.

[Very natural sounding, Alex -- just one small correction to do with singular vs plural]

How I found italki

I had English lessons at school for 6 years. After school there was a long time [I think you need something like "during which" or "in which" to connect these two parts of the sentence] I didn`t need the English language at all.
Now, I need to speak English in different situations related to my work. I want to learn English for private purpose [should be "private purposes"] too.
I started to learn English again some time ago. In the beginning, I only used the app “Babbel”. I recently discovered some other apps such as MosaLingua that provides [I can't explain why, but it seems like this could also be "provide"] expressions and phrases related to different job branches.
These apps are useful to learn words and phrases. They don`t help to improve your speaking skills very much. [This might sound more natural if the two sentences were joined, eg., "...words and phrases, but they don't..."]
I like reading books in English and listening to English audiobooks. I don`t catch every word and I often look up words or phrases in a dictionary.
I particularly like the British English. I have difficulties [would be better as "find it hard"] to understand American English when I watch a film.
The app Learning English from the BBC is very funny and helpful with short lessons and articles.
I have been listening to podcasts too lately. I like Luke`s ENGLISH podcast really well. You can learn words and phrases that occur in many different situations. His podcasts include very varied issues and topics both about every day live [everyday life] and more special stuff [I think this would be better as "specialized topics"]. He presents the podcast in a really funny and enthusiastic way.
Luke is an English teacher who does the podcast in his free time. He mentions italki, which is a sponsor, in almost every podcast.
And so I learned about italki. 

[A very nice notebook entry, Annette -- just a few suggestions for slightly more natural phrasing]

My grandpa (I wonder if the tense is correctly used) Thanks

My grandpa is a good chef. He lives in Japan. I wish he could come to visit every day because he tells good stories and makes his favorite dinner. I ask my mom to make the chicken that Grandpa makes. My mom says, “I will try ,but on one no-one makes it as well as Grandpa does." I watch my mon mom prepare the chicken. It looks tasty. When the chicken is finished cooking, my family sits down to eat. My mon mom was right. No one makes the chicken as well  as Grandpa does. The next time my gramdpa grandpa comes to visit, I tell him the story about my mon mom trying to make chicken. My grandpa syas says, “That is a great story.” Then he teaches my mon mom and me how to make chicken.

[Very well written and no problems with tense that I could see -- is there anything you were particularly worried about?]

There are companies that offer pre-written, or written-to-order, university assignments. Often they employ recent university graduates to write papers that current students can then pay for and submit as if it's their own work.