Mobs spawn waaaaaay too much

this is my first paper server and there is way too many mobs to play the game so im just looking for a way to reduce the number of mobs spawning.

You can edit the bukkit.yml. There are values that look (for my server) like this:

monsters: 80
animals: 5
water-animals: 1
ambient: 1

You can decrease these numbers to lower the spawnrate.

Thanks bro helped a lot.