Find heavy 5 rep set in 20 minutes .
Use 5-7 sets total.
You can do longer sets (6-8 reps) on first warm up sets, then last two sets before the main set can be for example (3-4 reps) so it may save power for the main set.

rest about 1-2 min bwn warm up sets, 1,5-2,5 min with the heaviest sets.
Also option is to do 5 reps all the time.
Be smart on these, dont lose your lower back / midbody control.