I have a question ,I don't remember whether I've commited a sin or not what should I do? Should I think I have done it?

What is Tawba Nasooh? How should it be made? What is the importance of Tawba Nasooh? How is Tawbatun nasuh made? How has Prophet Muhammad (pbuh) described Tawba Nasooh?

What are the essentials of repentance (tawbah) that we should consider to be accepted?  What are the conditions for an accepted tawbah?

What does istighfar mean? What are the virtues of istighfar?

If being sinner is written in my destiny by Allah, then why does He hold me responsible for my sins?

If we do something inherently right (ie. be truthful in a scenario where it may be difficult), is it recorded as a good deed or simply "not a sin"?

Could you give some information about the importance of tawba?

What does "sin" mean? Why does God create sins that lead people to the hell?