My grandma's party

Today is my grandmother's birthday and the entire family is happy about that, so we organized a party for her and I can see that she is also so very happy, (she still dances a lot). I thank God this that our family is so close and I hope we always will be like that.

I have to confess i don't even know how old she is but the only thing I know is I love her.

Watch your capitalisation, it is very important in written English. Also I have removed a number of commas. You don't often need a comma before "and".

My grandma's party

Today is my grandmother's birthday and the entire family is happy about that, so we organized a party for her and I can see that she is also so happy. (she still even dances a lot). I thank God this family is so close and I hope we will always be like that. this.

I have to confess that I don't even know how old she is but the only thing i know is i that I love her. (I eliminated the second "I know" from this sentence as it is repetitive)

Well done Caty!  I agree that you have to pay more attention to using capital letters when required as it is very important in English (unlike in Spanish)

I hope everyone enjoyed the party!