Is true that when we repent our bad deeds become good deeds?
Walaikumussalam w w
No, They do not automatically become good deeds. The matter is in the hands of Allah. If He wills he can change them, but He could also hold us to account as well.
It is through His grace that He has promised to accept our tawbah when we repent with utmost sincerity, remorse and with firm intention never to repeat that sin again.
We can’t be certain, because we don’t know the state of our repentance, whether it was proper and complete or not, whether it was acceptable or not. And then as well the matter is in the hands of Allah. He could still reject for deficiency in some conditions or for whatever reason.
Therefore, we should behave properly and always humble ourselves before the Almighty and His Majesty.