If you have just installed 3d Studio Max 2021 I recommend to make a couple of changes to the setting and user-interface. In my upcoming series "getting started in 3ds max" I am using exactly these settings. The following changes are made:
Turn off Ribbon
Chance System Units to METERS (customize/units setup)
Turn ON Auto Window under Scene Selection in the Preference Settings. (customize/preferences)
Resize the Scene Explorer on the left side of the screen
Increase the size of the Command Panel on the right side to fit two colomns.
Adjust the 3D snap: deselect Grid Point and select Endpoint
Turn on the Angle Snap Toggle (Keyboard Shortcut A)
Check if the Production Renderer is set to Arnold
In the System tab turn ON the "Legacy 3DS Max Map Support"