Upvote:3
To go to my university to get some document which will be of help in the future
Really? Is that the best you came up with in a visa application? I'm sorry to be blunt but you just wasted your hard earned money. That was never going to get approved that way.
Successful applicants spend a great deal of time or attention on applications to make a strong case. Those vague statements do not get visas.
Please consider reapplying only when there is a more convincing reason.
Even a non-visa national can not be so casual in a landing interview and expect leave to be granted, let alone a visa application.