I know it can be quite tough to go through all the difficult visa processes and have your visa rejected in the long run. The truth is that if they give the reason for your visa rejection as "doubts on the intention of your stay/study," then there are four likely reasons which I have already mentioned in my article. They either think that you have a poor academic background, your interview was poor, your language skills did not satisfy them, or there were inconsistencies with your choice of a study program. Go through these reasons carefully, and I am sure you will realize that at least one of these applies. Try to work on the ones that apply to you, and after you have tackled it, you can then apply again and hopefully, you can get a better outcome next time.