My Telegram Account Has Been Hacked

I was using Telegram on my Android phone and now I suddenly cannot log in to my account. Because of this, I suspect that my Telegram account has been hacked or accessed without my permission. I am currently completely unable to access my account and I do not understand how to recover it. I have important conversations and contacts in this account and I am very worried about misuse of my data. I request that my account be checked urgently, unauthorized access be blocked, and that I be guided clearly, step by step, on how I can recover my Telegram account and secure it again.