Do i need remade characters and objects if i want to make an original game? or can i make the characters in unity

Can i make and render and colour my characters and objects in unity and if so please tell me how

Unity is a game engine.

You write code in an IDE (e.g. Visual Studio), you prepare 3d assets in a modelling program (e.g. Blender), 2d assets in a graphics program (e.g. GIMP), and SFX and BGM in an audio editor (e.g. Audacity), and then you assemble them into a game in Unity. You do not create assets in Unity itself.

Short answer - yes you need to create them in software other than unity.

Long answer - What you need to use depends on the kind of game you are creating. Your budget also is part of this decision. If you’re making 2D art, you don’t need anything else aside from something like Gimp or Photoshop, or maybe a sprite maker software. If you’re making 3D art, you will need a 3D modeling/animation package, such as Blender/Maya/3ds Max. You might also want to sculpt, sort of like clay, using something like Blender or Zbrush.

Unity, unfortunately, doesn’t have any real useful art creation functionality. Some people have created art tools for use in Unity, but they are not made by Unity. One 3D example of this is ProBuilder’s Basic and Advanced tools.