Recently I tried to make a simple grenade, I was surprised at how difficult it was, I was unable to do it, I have been having problems with coordinating in general for a while, I wanted to know what I should study to improve myself with coordinates and be able to use with body movers and math efficiency, and velocity
I don’t think projectiles are a case of coordinates, Roblox’s physics should handle a lot of the issues you’re having.
If you know the maths behind it, it’s actually pretty simple, see this website for more: Projectile - Wikipedia
With these calculations, you should be able to apply a force using BodyForce objects and let the engine do the rest.
Hope this helps,
-Tom 
Here is another community resource for modeling projectile motion, no angles needed just vectors.
So i need study algebra and geometry?
Trajectory math and vector math could be used to make a grenade or you could probably tween the grenade (That would suck though)
One simple formula I’ve memorized is useful for getting the direction between two points, this can then be used to set a projectile’s velocity:
local power = 100
local direction = (otherPoint - origin).Unit*power
otherPoint being the target position, and origin being the start position for the projectile. .Unit gives it a length of 1, so we get only the direction basically. Then we multiply it by the power we want.
Super simple formula. I hope it helps a bit
Yeah i think that will helpme a lot.