Use a secure and privacy focused email provider (list of suggested providers).
Steps to change your email provider (to protonmail)
1. Register a new account.
Think about registering two accounts. One to use for personal and official affairs and one for spam (e.g. registering an account on an untrusted site).
2. Forward all incoming emails from your old email address/es to your new email address. (e.g. How to forward in Gmail)
3. Delete all emails saved in your old email account/s. If you want to keep emails, you can either copy/send them manually to your new email address or use the protonmail Import-Export app.
To use the protonmail Import-Export app you need a premium account. The cheapest way is to just upgrade your account to Pro for one month, which will cost you 5€ one time.
4. Change all your existing online accounts, newsletter subscriptions and etc. to you use your new email address/es.
I recommend to connect this step with the updating and upgrading of your passwords.
5. Delete your old email account/s.
Wait a few weeks/month before doing this. Maybe you forgot to change your email address somewhere important and still need the address active.