Dog is my friend

I decided to have to get  a dog in July,and I not choose  not to buy a dog. I adopted a dog from the internet. When the dog came to my home, her she was only one month old.
I am very like her very much. Because she looks like very cute and she always welcomes me when I get home. Sometimes I think a dog is  a loyal friend to humans. Dogs never mind that  I give her prize is very few prizes little.They can play with you on anytime even 2:00 am. I consider maybe haven't person can don't mind you call them on 2:00 am,
when I have busy work, I maybe can't give her a meal on time, but she is never angry with me and always licks my foot .I feel very happy. I imagine that if someday in the future I lose her, I might be very sad. This is the only one bad thing in having  a pet.

Her She is always naughty too. She likes biting my slipper and bite or my bed sheet. it's make me very headache. Its give me a bad headache. I don't know how to educate her.

Notes: I understand what you meant by your writing, although it has some things that I have corrected, you have communicated in your new language. That is a very good thing !

to have a dog -- that sounds like the dog is going to be a meal. English writers would use something like "to get"/"to buy"/"to obtain" or even something like "to become a dog owner".

not choose -> choose not to buy.   The difference here is that you had a decision, the decision was "to buy" or "not to buy". Not choose is incorrect for that reason.

I am very like her -- this sentence is saying that you   look very much like the dog -- you really meant that "you like her"

I have changed a number of yours tense and very construction -

welcomes -- the act of greeting

have a pet -- having a pet

The difference between "she" and "her" 

she indicates a female person.

her indicates ownership by a female

similarly

he indicates a male person

his indicates ownership by a male.

 he/she/her/his/  are problems for a number of Chinese speakers that I know so be encouraged that this is not a problem unique to yourself. Even really, really good Chinese speakers of English make this mistake.

On the whole, you have done well, I understood your pride and joy in your pet. So quite a good effort !

Dog is my friend

I decided to have a dog on July,and I not choose to buy a dog.I adopted a dog from internet.when the dog came to my home,her was only one month old.
I am very like her. Because she looks like very cute and she always welcome me when I get home.Sometimes I think dog is loyal friend to human.Dogs never mind I give her prize is very little.They can play with you on anytime even 2:00 am.I consider maybe haven't person can don't mind you call them on 2:00 am,
when I have busy work,I maybe can't give her meal on time, but she never angry with me and always lick my foot.I feel very happy.I imagine if someday in the future I lose her,I might be very sad.This is only one bad thing in have a pet.
Her always naughty too.She like bite my slipper and bite my bed sheet.it's make me very headache.I don't know how to educate her.

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My dog is my friend

I decided to get a dog in July, and I choose not to buy a dog but adopt one from the internet instead. When the dog arrived at my home, she was only one month old.

I really like her because she looks very cute and she always welcome me when I get home. Sometimes I think dogs are loyal friends to humans.  Dogs never mind if I only give her a little prize. Dogs can play with you at anytime, even 2:00 am! I don't think many people would like you call them at 2:00 am!

When I am busy with work, I might not be able to give her meal on time, but she never gets angry with me and always licks my foot.  I feel very happy right now but I imagine if, some day in the future, I lose her, I might be very sad. This is only one bad thing about having a pet.

She is always naughty too. She likes to bite my slippers and to bite my bed sheet. It really gives me a  headache. I don't know how to educate her.