If you want to add more security to your Mastodon account, you can set up a system called "two factor authentication" (also known as 2FA). This prevents anyone else logging into your account even if they find out your email and password.
2FA works using a special app on your phone which gives you a short code number to type in when you log in.
I've done a non-technical guide all about 2FA and how to use it, including answers to many questions:
➡️ fedi.tips/using-two-factor-aut…
Using Two Factor Authentication (2FA) on Mastodon | Fedi.Tips – An Unofficial Guide to Mastodon and the Fediverse
An unofficial guide to using Mastodon and the Fediversefedi.tips