Generall guide to improve stamina
General session guide for a slightly less intense exercise to improve stamina. Try to reach an intensity level of 60% (researched) of your max (calculate 1RM) so you keep your muscle mass.
Observe that with stamina improvement we mean the muscular stamina. Endurance is described in another session guide.
Number of exercises
More sets, more repetitions. Think extra about technique and intensity here so you end up in repetitions with a good execution. Then the stamina improvement will come.
You will probably feel a burning sensation in your muscles here so it is extra important to rest enough to keep it sustainable.