Unfortunately high school students are not eligible for our bachelor level summer courses.
However, for very motivated high school students we sometimes make exceptions. Therefore, I suggest you send an e-mail to the course leader of the particular course stating your motivation to participate in this course. Then, he or she will be able to tell you whether or not it is an option for you to apply. For the language for example, it does not have to be a big problem if you are a bit younger/don't have a bachelor level.