A problem with your code is not an issue (= a bug in the kata). You may find some help in the official documentation: https://docs.codewars.com/training/troubleshooting/

ValueError: invalid literal for int() with base 10: '-'

This means that at the line 38 of your code, you try to do int(-), which is incorrect.

Traceback (most recent call last):
File "/workspace/default/src/codewars-test/codewars_test/test_framework.py", line 111, in wrapper
func()
File "tests.py", line 37, in random
test.assert_equals(seven(n), sol)
File "/workspace/default/solution.py", line 38, in seven
conv_back = int(remaining_number)
ValueError: invalid literal for int() with base 10: '-'

my code is passing all the tests except this one, it seems to have characters (n,sol) instead of numbers(x,y) as a testcase. What am i supposed to do with this? Ive tried isinstance(m,str) but thats not working.