Then don't use numbers. Numbers will lose precision in high inputs so it will fail. It's exactly the purpose of this kata. Which is why the description told you to return a string. You have to implement your own addition algorithm.

I'm closing this since this is not a kata issue.

I'm trying to convert number to string to match the test, I used every way on earth to convert it and it's only giving me binary numbers witch never passes
please reCheck the test envieronment, and convert the last answer to number instead of string.