Before the end of the lecture week 6, you can always resubmit any of your previous solutions. Just fix your code, run
./grading do again, and commit and push everything to GitHub.
Resubmissions are always safe. You will get a new score each time you resubmit, and your final score for each task is the maximum of the scores from all weeks.
Just note that for many tasks, you will get the highest points if you solve it early. Lower points apply to both resubmissions and late submission.
The course stops after the lecture week 6. No submissions of any kind are accepted after that.