If you yourself try to log in to your Google account using your own laptop in a coffeeshop or hotel, for instance, that's several states away from where you typically use that laptop to log in you will get "unknown device" warnings and be asked to verify your account by supplying either your backup e-mail or phone number that you gave to Google. That's after you've already provided the correct password. Even if you can do that you will get e-mail messages very shortly afterward from Google asking you to confirm it was indeed you.
I don't know what you're using to make the statement, "they managed to access my account multiple times," because Google has had the system it uses in place for several years now. It is common practice to collect e-mail addresses and then to send out spam using those e-mail addresses as spoofing addresses.
You need to be a lot more specific in what you mean by "hacked." An attempt to access your account isn't hacking, though it could be an attempt at hacking. It could also be someone with the account that is one character off yours fat-fingering their account name at login and making multiple attempts before realizing their mistake.
Brian AKA Bri the Tech Guy (my website address is in my profile) Windows 10 Home, 64-bit, Version 1709, Build 16299
Here is a test to find out whether your mission in life is complete. If you’re alive, it isn’t.
~ Lauren Bacall