Gmail is a great service for sending e-mails, but it can happen that the e-mail service does not run smoothly. For example, it sometimes happens that emails are no longer synced properly within the Gmail app. In such a case, it is best to reset your Gmail account.
Problems that arise when Gmail stops syncing properly include, for example, you can no longer send or receive emails, emails hang while sending, emails can't be opened, or the Gmail app is very slow. You may also receive a notification that the account is not synchronized.
If you have such problems with Gmail syncing on your Android phone or iPhone, you probably need to delete your Google account and reset Gmail. However, it's a good idea to make sure you have enough storage space first, and then update the Gmail app itself to see if that fixes the problem. Then restart your Android smartphone or iPhone.
delete google account
On your Android smartphone or iPhone, within the Gmail app, go to Settings / Accounts / Google / Google Account and press your account. You will then see an overview of all data from Google that is synchronized with your Android device. Press the menu button at the top right and select remove.
Then the data of your Gmail account should be cleared in the app, so that you are not left with anything that could cause problems.
On your Android smartphone, go to Settings / Apps / All apps / Gmail and press the button at the top of the list Stop now and then on Switch off. Then the Gmail app will be factory reset.
On an iPhone, in the Settings app, go to General, iPhone storage and then tap gmail. Here you will find the option Delete app. Then download the app again.
Open the Gmail app and add your Google account again. Gmail will then start syncing your emails all over again.