Belgium

Hello,
I'm from Belgium, this is a little country in Europe.

Better is: I'm from Belgium, a little country in Europe.

I live in the Brussels capital.

Put: "I live in Brussels, the capital (city)" or "I live in the capital (city), Brussels". "City" is optional.

 
Here, the specialty is chocolate, fries and the beer. No need for "the". Put "...and beer"

It often rains during the year, fortunately, the summer the sunshine is coming.

Better is: "It often rains during the year. Fortunately, there is more sunshine in the summer".

The general atmosphere is nice since the World Cup of football.

"Nice" is weak, though English speakers use it all the time. Use a more exact term like fun, electric, upbeat, etc.

 
The new team which is forming is very appreciative of the supporters.

Probably "its supports" is better and more precise.

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The essay is perfectly understandable and makes me want to visit Belgium again. My favourite (UK spelling) Belgium food is moules-frites (mussels and French fries) with a Belgium beer.

Belgium

Hello,
I'm from Belgium, this is a little country in Europe.
I live in the Brussels, the capital.
Here, the specialties y is are chocolate, fries and the beer.
It often rains during the year, fortunately, the in summer the sun shines is coming.
The general atmosphere is nice since the football World Cup of football.
The new team which has been formed is forming is very appreciative of the supporters.

Belgium

Hello,
I'm from Belgium, a small country in Europe.
I live in the capital city of Brussels.
Here, the specialties include chocolate, fries and beer.
It often rains during the year. Fortunately, the summer sunshine is coming. 

The general atmosphere has been nice since the World Cup of football.
The new team being formed is very appreciative of its supporters.