From your Gmail account, you can choose to integrate your signature immediately and automatically each time you write a new email.
1️⃣ Access your gmail settings
To do this, from Gmail, go tot the settings then See all settings.
2️⃣ Access your general settings
From the General tab, you will find the options concerning your signature at the bottom of the page.
Tick the checkbox : Insert signature before the quoted text in replies, and remove the '--' line that precedes it.
That's it !