Running

If you would like to comfortably run for example 6.15 for say one or two minutes, then you need to train yourself such that 6.15 is not close to your top speed. To do that, you need to repeatedly run significantly faster than that. For example try 8 times 30 or 60 seconds at 6.00 (or faster if you can) with a minute of rest between. Make sure you are warmed up, and perhaps take it a bit easier on the first two reps.

Should I run my efforts faster and my recovery slower?

Yes and yes.

I sympathize since it's really hard to know without a reference, but 5k pace is supposed to be pretty darn quick. It's not a 5k that you're doing just to finish, it's a 5k that you're doing as fast as you can.

Recovery should be between 50% and 75% of your 5k pace, so if the fastest you can run a 5k is 6:15/km, then your recovery should be around 8:20/km or slower. You might feel like you're plodding, but you're supposed to plod after working hard. It's a distinct difference.

Are you using the guided run option on NRC? If not, I recommend it. I just finished the Next Long Run (the one immediately after the Fartlek Run) this morning. I’d say as long as your 10k pace is more effort than recovery and 5k is more effort than the 10k, you are doing fine. Just getting out and doing the run is a success!

Edit: I just noticed your post was a month old! I only found this magazine today. Hopefully your running is going well!