Hello there

Today I'm here just to join you, guys. Lately I feel ashamed about my English and it's time to do something about it, because it's like "Well.. You know.. So.." Not impressive. Hope to find here a little help and experience. :)

You found the right place, Oz.  Just pay attention to the sentence structure and words that I corrected, and keep practicing.  Good luck :)

Yesterday was a happy day.

Yesterday was a Chinese traditional festival called "Winter Solstice."  In China,especially in Guangdong and Fujian Province,the importance of Winter Solstice is only second to the Spring Festival.  People usually go home and stay with families during this festival.
Although I really want to go home to see my dear parents, but I was at the university and had no time to go home.  Many of my classmates were in the same condition.  Consequently,in order to celebrate Winter Solstice, we ate hot pot together, just at the big balcony in front of my dormitory.  We bought various kinds of foods in the afternoon and started our big meal at about 5pm.  What is worth mentioning was that the glue pudding, which was one of the traditional foods during Winter Solstice. was so delicious that I even burnt my tongue because I ate it too quickly.  Everyone felt happy last night.  Though we couldn't stay with our families, we still felt happy and warm during this Winter Solstice.  :)
By the way, all of us had a lot of fun during the game "truth or dare". O(∩_∩)O~

Very well written, Elle!  I just made some minor corrections through your sentences.  Be careful to use spacing between sentences.  Also, when expressing a time period, many times it is better to use the word "during."  I included a few examples in my correction.  You're doing very well writing paragraphs.  Keep up the good work.  :)

hello guys

if everything does n't kill me...it makes me more powerful

Better to say:

"What doesn't kill me, makes me stronger."  -Nietzsche 

It's not a good idea to "everything" this way, better to use the connecting word "what."  Also, we like to use the word "stronger" in this case, in place of "more powerful."

An Brief Introduction to Xi'an

Xi'an is a beautiful city situated in the middle of China. With a history of more than 3000 years, the city is surrounded with time-honored atmosphere.

The first time I came to Xi'an was when I went to my university 5 years ago. As soon as I got off the train, I was astonished by the amazing scenery: beautiful long walls, straight-forward streets, modern high-rise buildings and fantastic historical museums. When I entered to the Shannxi History Museum, I was attracted by the amazing amount of precious items of historical value.

Apart from the incredible scenery, the people in Xi'an are always helpful and hospitable. If you have any question about the way to go, the local residents will give you a satisfying answer. In that regard, Xi'an can feel like home constantly.

However, the drawbacks of Xi'an are also various, from the stuffy air to the crowed streets, and from the bad infrastructure to the disturbing drainage system. It is like all coins: they all have two sides.

I like Xi'an not only because of the unbelievable view, but also because of its hospitable residents. Although there are some unsatisfying things, the memory and the expression are of sentimental value.

Very good!  Just a few small corrections in blue.  Keep practicing!

My nieces

The challenge of the day is making comparisons in the sentences. I have got two nieces and they are twins, but they aren’t identical. Their names are Lénia and Lara. Lara is more playful and good-humoured than Lénia; however Lénia is taller and more energetic (you can say "with more energy" here, but I like "more energetic" better) than her sister. Lara has a stronger personality, and Lénia is more amiable than Lara. However, both are very cute and happy children.

Very good, Ana Cristina!  Just have a look at my comment regarding the words "more energetic."  I think you might prefer to use this expression.  :)