Frequency vs Intensity

Rosylee1976

So I am just getting into exercise at just under 300 lbs. I have already lost about 40 lbs. Have another 160 lbs to lose. For those who are knowledgeable about exercise, I would welcome some advice. My goal is ultimately to lose fat, building muscle is a secondary benefit. So in relation to the treadmill, would it be better to walk for longer at a lower speed or higher speed but shorter time. I can onky manage about 25 minutes at a higher walking speed, well high to me anyway. Also, with regard to strength training, is it better to do more reps at the lowest weight, or do 2 sets at a weight that you can manage. Hope this makes sense. Thanks