Secure your Telegram account by adjusting privacy settings. This mainly includes limiting profile visibility, enabling two-step verification, and setting up account self-destruction.
This is the most important step. Telegram requires a phone number for signup, and by default, it’s visible to your contacts. If you allowed Telegram access to your contacts, they’ll see your number. To stay anonymous, set number visibility to “nobody” — this hides it from everyone and prevents the others from linking your number to your handle. And, of course, do not set your real name in your profile or username.
Limit exposure by setting “Last Seen & Online” and “Profile Photos” to “nobody”. This keeps others from viewing your photos and knowing when you're online. Furthermore, by setting Forwarded Messages to “nobody”, no one can find you back from a forwarded message from you.
Add a cloud password to prevent unauthorized access, even if someone gets your SIM card. Go to Settings > Privacy and Security > Two-step Verification, and use a strong, unique password. You could further enable the Passcode Lock, which the Telegram application itself will require to open.
For extra safety, enable auto-delete for inactive accounts. Set it to 1 or 3 months to ensure your data is erased if you lose access to your device.
Device section shows from which devices you have logged onto your account. Remove old devices/sessions where you do not use Telegram anymore.