Europe

Yes, I have travelled to Spain, Croatia, Finland, France, Austria, Italy, Greece, Denmark, Portugal, Netherlands. I travelled to all these countries by train, by plan, sometimes by car. However, I prefer to travel by plane or train. :-)

Have you travelled...?

I have travelled... (It means "It's a part of my life", not just "a memory of the past" )

Agree with Andry's corrections. Good job!

 Use "have done it" stucture when you are talking of non-specific time, your life experience, but use past simple when you refer to a particular time, a particular journey:" I travelled to Spain two years ago".

Yes, I travelled to Spain, Croatia, Finland, France, Austria, Italy, Greece, Danmark, Portugal, Netherlands. I travelled all this countrys by train, by plan, sometimes by car. However I prefer to travel by plane or train. :-)

Yes, I travelled to Spain, Croatia, Finland, France, Austria, Italy, Greece, Danmark, Portugal, and the Netherlands. I travelled to all these countries by train, by plane, and sometimes by car. However, I prefer to travel by plane or train. :-)

travelled = British spelling; traveled = US spelling

"have traveled" sounds a little better, but what you have written is correct. In the second sentence, "I traveled..." sounds better than "I have traveled..."

We usually say the Netherlands or simply Holland.

A few small errors, but generally well done.

Yes, I travelled to Spain, Croatia, Finland, France, Austria, Italy, Greece, Danmark, Portugal, Netherlands.
I travelled all this countrys by train, by plan, sometimes by car.
However I prefer to travel by plane or train.

My suggestion:

Yes, I have travelled to Spain, Croatia, Finland, France, Austria, Italy, Greece, Denmark, Portugal and the  Netherlands.
I visited all these countries by train, by plan and sometimes by car.
In general I prefer travelling by plane or by train.

Well done - thumbs up!