Panels ligthroom

In a first step try is to reset the preferences to the default settings.

• Reset Procedure:
• Close Lightroom.
• Windows: Hold down [Alt]+[Shift] while restarting Lightroom.
  Mac: Hold down [Opt]+[Shift] while restarting Lightroom.
• Overwrite the Preferences when prompted by the dialog.
• Close Lightroom.
• Restart Lightroom.

It's recommended to backup your preferences before you reset the preferences to the default settings: 

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

Are you running LR in French, German, or Spanish, and the sliders in the Masking panel are cut off on the right, like this:

If that's not your issue, then please provide much more detail, as requested by GoldingD.

????

Not a clue what you are referring to.