Is it normal to have these white lines at the edges that seem to be cut of?

Nope, it’s not. Try updating the watch to the latest WatchOS version available, if that doesn’t help, then try restoring it to factory default settings and set it up as a new device. If all else fails, you might have to take it to the Apple Store.

What is the WatchOS version on this?

See if you can get a new Series 7 or 8 at a price closer to the SE 2nd Gen, imo that will be much more worth it.