Expected }, but its already there?

Questions & Answers
1

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public Interface IDamageable
{

public void Damage(float damage);

}

it says error CS1513: } expected
but its already at the end, even in visual studio it recognizes it!
(sorry if the text looks confusing)

3

The error message you were provided is odd, since there was a specific problem, and that wasn’t it.

The more appropriate error message to see would have been:

The modifier ‘public’ is not valid for this item

With that in mind, some useful reading on the subject can be found here.

Additionally (prior to C# 8), an interface can only contain public functions.

By extension, an interface itself can only be public if it’s external to another class.

public class Test : ITest1
{
	// This must be public to fulfill Interface requirements
	public void Func(float value)
	{
		// Implementation
	}
}

public interface ITest1 // MUST BE PUBLIC
{
	// The function template must *not* specify accessibility
	// and will always need to be used as "public" in a class
	void Func(float value);
}

… or, to demonstrate private interface implementation…

public class TestBase
{
	private class Subclass : ITest2
	{
		public void Func(float value)
		{
			// Implementation
		}
	}
	
	// This *CAN* be private because it's contained within a class
	private interface ITest2
	{
		// This still must not specify accessibility,
		// and will still be "public"
		void Func(float value);
	}
}
2

public void Damage(float damage) { }

You’re declaring a method like a variable.