probably depends a bit on your course, if you're doing a STEM course with 25 contact hours it's going to be much harder than english with 5 contact hours!
personally I think we can generally fit in a lot more than we think if you're careful with time management and happy to get up early and be constantly on the move but that does sound a lot... perhaps start off trying to do it all but have a plan for what you would give up if you need to?
I mean you already do sports so know how much time you need there, I'd imagine debating would not require a weekly participation if you were tight on time and you could probably just attend debates you were interested in, there's no actual guarantee of getting a job although that might be tough as you'd probably have to take the hours you were given, applying for placements can fit in as and when just like studying, the issue you will have is taking on too much things which take place in specific time slots as then they are likely to clash