Stonehenge

Corrections: 

I took part in a two-week Eurocenter course

in English, we do a lot less of "a dress of the girl" and do more of "a girl's dress" or (with things of objects) "a University course" or "a museum exhibition."

I think travelling to another country is really the best way to improve your ability in a language, regardless of the language you want to learn. 

You can't improve a "language" [or "art" or "architecture"] but you can improve your skills/ability/competency/capacity in that subject.

As a part of the program, we traveled to some attractions in England.

a.) Program - yep, spelled Programm in German :-)

b.) You used past perfect tense. Native English speakers generally use past perfect tense ONLY when they are talking about 2 things that happened to refer to the thing that occurred first. Using it normally emphasizes a result of that action. An example of that would be "Last summer I decided to study in London. I had traveled to England previously as a child and liked it alot" or "When I was in Germany, I had seen Arabic Calligraphy in the Pergamon Museum. I later began studying Arabic."

 I was surprised by how [small] it was. In the photos...

Suprised + by + thing/event/person. 

Little is not grammatically wrong but just reads wrong. Maybe there is a difference in British English, American native English speakers typically do not use little to refer to object size... it's only really used in things like Childrens' books, to describe children "what a cute little baby! Sweet!" and to generally quantify amounts of feeling "I felt a little sad." or things "just a little bit of that Quiche, please! No! That's wayyy too much!!" 

We use the word "in" with deceptive art, including photos, magazines, books, paintings, movies, etc.

"The landscape in the painting." "The woman in the drawing" "The house in the photos" "The room in the magazine" "The story in the book" "the article in the newspaper."

Stonehenge

*very old

*while we were there

Stonehenge