Q. Are there Colleges/University's in Japan where non fluent speakers can apply to? (something like an international college)
A.Yes, google is your best friend in this case
Q.And how hard is it to be accepted into one?
A.Getting into the university itself is not very difficult (As a foreigner), yet dealing with immigration will be a bit complicated.
Q.How much does the average University in Japan cost?
For your first year expect to have ¥834,800 ($7,860 or €4,940). This includes matriculation fees, tuition fees, and entrance examination fees. Each year after the first year is cheaper, seeing how your only pay the examination fees and the matriculation fees once.
Please note that regardless of how much the universities cost, Immigration requires you to have around $15,000 (€9,400) in the bank, or promises of that money from family.
Also, the prices listed above are for national Japanese universities. International universities cost more from what I have noticed.
Q.Am I beeing a complete fool for wanting to study there or is it actualy realistic xD?
Absolutely not. Going to a University in Japan is 100% possible, regardless of what others may tell you.
Save money and learn Japanese before going to Japan. Below is a link with information on how to learn Japanese fluently. To save money, you could either rob a bank (not suggested...) or get a job.
All Japanese All The Time Dot Com
With more info on being a student in Japan, check out the following link.
Student Guide to Japan-English and Other Languages-JASSO