How do i make a mob that spawns other mobs with a timer

It means you used the "on every tick" trigger of your entity. I advise you to create a global variable that store a number.

Each time your procedure is called, you update the variable. If the variable reach a certain number (60 tick for 1 second I believe), then summon the creature you want and reset the variable to 0. Else, just add 1 to your variable and do nothing more.

PS : Check carefully that your variable is global and not local. You have a specific tab on your workbench to define them. If you create a variable directly in the procedure tab, it will be local and not global.