Simple calculator which can operate on more than two numbers
reduce

Whenever you need to fold an operation across a list, like you're doing, you want to use reduce(). That takes a function, an iterable, and an optional initializer, and performs the operation across all of them. So:

reduce(f, [x, y, z])


is equivalent to:

f(f(x, y), z)


This is precisely what we want. The operator library additionally gives us all the mathematical operators, so we don't have to write them ourselves. So the various operations are:

+: reduce(operator.add, numbers) # or just sum(numbers)
-: reduce(operator.sub, numbers, 0)
*: reduce(operator.mul, numbers)
/: reduce(operator.floordiv, numbers, 1)


Simplifying the logic

We could directly translate the above into a dictionary of operators and a dictionary of initializers:

operators = {
    '+': operator.add,
    '-': operator.sub,
    '*': operator.mul,
    '/': operator.floordiv
}

initializers = {
    '-': 0,
    '/': 1
}

result = reduce(operators[operation],
    numbers, 
    initializers.get(operation, None))


This will additionally fix your bug where for subtraction you're really adding. 

List Comprehensions

It's more direct to simply initialize your numbers directly:

numbers = [int(input("Number: ")) for _ in range(amount)]


Note that x is not a good name. Prefer more descriptive names. 

Division

All of your numbers are ints. Which means that when you divide, you're going to end up with 0 as soon as you have any number that isn't 1. That isn't particularly interesting, so I'd suggest using floating point numbers instead.