Please correct it

So I wake woke up and my mom told me that my sister was coming over. I just don't didn't understand why I have had to wake up because of my sister. She said that I have had to help her to clean up the house.

My sister have has two children, one is 12 and the another is 2.

She lived with us until last year so when she got married and moved to her own house. Sometimes she comes over to see how my mom is doing.

I like her. I mean I'm not that close to her, like best sisters but she's nice. We used to go out and (Who's?) 10th birthday we went on

a trip and It was expensive hehe. My mom was never a person who liked to go out, even to travelling she didn't like. So she didn't come with us.

But I liked it. Each day we went to different beaches and different places.

But it was years ago.

As you began the story in the past, be careful to continue with the same tense.

I made a few sentences in here.Will you help me? Thanks in advance .

The girl doesn't care the repercussions of being with that guy who was behind the bars for years.

(Usually we use repercussions as a plural. Also, the expression related to prison is simply "behind bars", without an article.)

Stagnant

Today I felt so stressed about my life that the circumstance is stagnant for as I cannot find someone to express the mourning of her my grandmother.

(Note that as you use "that" you need to include "so".)

Keep in mind here that we are looking at a character who might not speak with perfect grammar, such mistakes are common even with Native speakers. 

In terms of correct grammar, "there are lots of flavors" would be correct, but then when speaking about a list of singular items, "there is" is fine, so "there's Rocky Road, etc"

This is very formal and you won't hear much of this on the high street (even in Kensington!)

Bother is a word I would often use if asking for information, "Sorry to bother you" is a good line.

"No trouble at all" you rarely hear, "It's alright" would be my typical response. And instead of "It's quite a distance", a simple "It's quite far" is more likely (I often say "It's a bit of a trek" - an idiom from my home region, but it confuses Londonders).

The second half you would hear, though an Englishman is more likely to say "cheers" and the answer "no worries" is one of many possible responses. Slang like this is regional, of course, but this is what you might hear on a London street.

I can't speak for CNN but as a native (albeit slightly older) even I have trouble with Instagram comments. It's a language unto itself!

How do you manage with BBC news? I would consider that a better source of authentic writing.

My Niece

Note the difference between British and American English, with regard to the subject ~Mathematics. In the US it is abbreviated as Math, in my native UK we use Maths.

Hope this helped!