My cCat.

Title should always be capital.

I have a cat, it his name is Liếm.

I don’t know where does ithe coame from?.

This sentence isn't a question, no need for the question mark.
Liem is a male, so you can call him he.

ItHe appeared in front of my house one month ago.

When I saw it, I havewas a little reluctant because atin my country, everybody says that “When Ca cat comes home, it is poor, D. When a dog comes home, it is rich”.

'Saw' and 'Was'; you're talking about the past.
Also remember your commas.
'It is poor', not 'is poor'.

After a minuete, I decided that I would feed it then. I brought some food to the cat.

No need for 'then'. Also, after 'feed it', start a new sentence.

It ate like a horse, It was; it seemed so hungry.

The past of seem is 'seemed' not 'was seem'.
Remove the comma and put a semi-colon, or a fullstop and end the sentence.

Now, I think my decide ision was right because my cat is so cute.

Was, not is. You're talking about the past.

It is always follows me and jumps onto me.

You can also say 'he' instead of 'it'.
'Follows' and 'Jumps'. You're only talking about one cat, not more. If it was more then you would use 'follow' and 'jump'.

I would like to seewatch my cat, especially when it sleeps.

It appeared found him in front of my house one month ago.

Assuming that your cat is a male-- if it's a female, you'd use "her".