Weekly challenge too hard

For the first time I am struggling with the weekly challenges:

• Finish 5 Matches having more Kills against your Nemesis than they have against you: Everytime I finish a round my nemesis has like twice as many kills as I do. I am not sure what I need to do to beat this challenge.
• Get 3 Triple Kill Medals (3 rapid Kills) or better with an SMG: I'm not typically a rush SMG player. I did try to play Nuketown with an SMG but was lucky to get 2 rapid kills let alone 3.

What am I doing wrong? Any suggestions for map types, perks, loadouts etc.