Sorry that Photoshop 2018 keeps opening a new version of itself whenever you open a new file.
Would you mind sharing your operating system version? Also, why are you using an outdated version of Photoshop. Please share the report from the Help> System Info menu in Photoshop.
To get started, please try resetting the Photoshop preferences: Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (Mac OS) as you start Photoshop. You are prompted to delete the current settings. The new preferences files are created the next time you start Photoshop. See: https://helpx.adobe.com/au/photoshop/using/preferences.html