How do i improve endurance?

there's no treadmill in my gym, only bikes ,

when i've been into bodybuilding i noticed a huge difference in my endurance,
from playing basketball 30mins. straight, to playing barely 5 mins. horrible......

(i'm gaining mass)

some people say if i try to improve endurance i'll have to give up some bodyweight,

how do i improve endurance? without losing mass?

thanks a lot!

i found endurance to mostly be a mental thing so just do something that is tiring for 30+ minutes and eat to compensate

i would recommend jogging outside, etc.

I'd also definitely recommend jogging outside. So many people seem to have forgotten that you can actually just walk out your front door and run, and seem to think that the only way to do cardio is in the gym!
My current workout has been targeted at building endurance, and I haven't sacrificed any mass. It consists mostly of supersets.
So a typical Monday would like as follows:
Squat - Reps - 15,2,12,2,10,2,8,2 (the higher reps are at about 60% 1RM, and the sets of 2 are around 85-95% 1RM)
Calf Raises/Single Leg Box Jumps - 4 sets of 16 and 12 reps respectively
Goblet Squat/Wide Squat - 3 sets of 12 and 12 reps respectively
Donkey Raises/Straight Leg Deadlifts - 4 sets of 20 and 12 reps respectively
Any other business (i.e. single leg squats, hamstring curls, single leg deadlifts, box jumps, squat jumps etc)

This type of routine mixes strength work with endurance that helps you build yourself in both ways, whilst adding functional training that should help you as an athlete.
Hope this helps.

How out stepping outside of your air conditioned bubble and let the sun caress your pale body? Doing cardio won't make you shrink unless you are in a calorie deficit. Just replace the lost calories and you will be fine.