For all SQL beginners here, there are multiple very decent, FREE websites to learn SQL commands. For people who are bit more advanced, check out SQL murder mystery, its great.

I think there should be an example where a term of the sum is divided more than one time. For example:
k-divide(8, 2) = sum(1, 1, 3, 1, 5, 3, 7, 1) = 22
The first time I didn't catch the part about repeating the operation, as the instruction mentioned dividing twice. My fault, but I think the it could be rewritten clearer and shorter. Maybe

For each integer from 1 to N, perform the following operation:

1. If the number is divisible, divide by K, and repeat
2. Otherwise, end the operation

Like others said, some code solves this kata in 1 second. So it CAN get optimised.

It doesnt fail your random test, your code supposedly is just unoptimized and takes too long to calculate, like my code, but I dont see a way how to optimize my code even further

My solution passes all the 63 tests, but fails the random tests.

Like said, it doesnt get much more optimized than it is rn

Your code is too slow for this problem. Large values of N (up to $10^{18}$) are tested and your solution should be able to handle such values.

Author's solution passes all tests below 1 second. Are you sure that your code is optimized at all?

The servers are too slow.... and I think my code doesnt get much more optimized than it is

Execution Timed Out (12000 ms)
Why did my code time out?
Our servers are configured to only allow a certain amount of time for your code to execute. In rare cases the server may be taking on too much work and simply wasn't able to run your code efficiently enough. Most of the time though this issue is caused by inefficient algorithms. If you see this error multiple times you should try to optimize your code further.