How to open forgotten pattern

If you don't care about the data you could hard reset the phone in this way it will clear everything. Of course you will need to re-enter your google email account and password to verify that the phone is yours.

Hard Reset for S9+

1. Hold down the Power key + Volume Down for a few seconds to hard switch off/restart the mobile.
2. Plug in cable to PC.
3. In the second step start pressing Volume Up + Bixby + Power button for a couple of seconds.
4. Let go of all buttons when the SAMSUNG logo appears.
5. If you see Android Robot with "No command" tap on the screen.
6. After that select "wipe data/factory reset" by using Volume buttons to navigate and the Power key to confirm that.
7. In this mode choose "Yes -- delete all user data". Use Volume keys to scroll down and the Power button to accept it.
8. Finally select "reboot system now" with the Power key.

Good Luck!