Create Telegram account with a phone number without associating with your identity.
Add a "username". Share "username" instead of "phone number" to others.
There are a lot of options inside the "Privacy and Security" page.
Never let other search you by phone number. A simply computer program can search telephone numbers one by one easily. Choose "My Contacts" or "Nobody".
You may not want other knowing your online state, or even worse, knowing you by observing the state and people using phones nearby. Set to "My Contacts" or "Nobody".
If you use your face as profile photo, and set to "Everybody"...
Your messages may be forwarded. If you don't want your profile is linked with the forwarded messages, please select "Nobody".
People nearby may observe your location if your phone rings. Select "My Contacts" or "Nobody".
This option is up to your choice.
Choose the shortest time you consider acceptable for "Delete my account if away for". Even you cannot touch your phone for a period of time, the time your data at risk could be limited.
Choose "No perviews" for map and link. Loading previews may leak your IP address, online state, etc.
Under certain condition, network may be a rare resource. Try to limit the use of network by not downloading media.