English, this strange unknown..

I think English is a beautiful language but it is very difficult to learn unless (or "difficult to learn if you want to...") if you can speak it with others.
The construction of the phrases are is (the verb does not match the preopositional phrase "phrases", it matches "construction" which is singular) very different from Italian.

Ben fatto!  You tried to make really difficult sentences! :D

English, this strange unknown..

I think English is a beautiful language but very difficult to learn unless you can speak it with others.
The construction of the phrases is very different from italian.

(I'm not sure this is what you meant, but it's a simple change that makes sense.)

English this strange unknown..

I think English is a beautifull language but very difficult to learn if you can't speak it with others.
The construction of the phrases are very different from italian one.