他去过世界上几乎每一个国家

He's been to almost every country in the world.

He has visited almost every country around the world.

He has been to almost all countries around the world.

He has been to almost every country all over the world 。almost应该用来修饰country所以放到那里而不是has后面。

He has almost been to every country all around the world

He almost have gone to every country in the world.