Help me how to create simple physics

Hi im young dev from north europe, english not my mothers tongue so sorry for mistakes

I have used unity to make few games in past but i want to learn more physics and game making, i made simple asteroid shootrers and arkanoid etc games already with xna. i dont want to use physics like box2d because then i dont learn how to make them myself

Now i want to make simple physics game, like golf, ball throwing,
i want to be able

  • control gravity
  • detect if object is in ground or in hill
  • detect if its in air and hits corner and make it fly in another direction

I made drawing because I’m bad at explaining in english

do you guys have any tutorials or help or physics examples?
thanks for any help really appreciate it