Failing 4th as level

Im currently in my first year of a level and im taking 4 as levels : Chemistry biolgy maths and psychology however im certain that I want to drop maths preferably before my as exams but if not after ,and carry on with my other 3 subjects so if i get really good grades in my other 3 subjects and fail maths will this ruin my chances of getting into a good university or will this failed as level look bad on my application?

If you are applying for courses that ask for three AL grades and don't require Maths, a weak grade in it won't make any difference at all, unis would just look at your three highest grades.
That said, in many cases it is better to drop the 4th subject and focus your time and effort on the others.