I recommend taking a look at my 
Sensor Light Blueprint.
First, you’ll need to set up a trigger. If you’re aiming to run this at night, create a schedule helper that starts well before dark and ends at the time you’d like it OFF. If it’s meant to run 24/7, create a toggle helper instead. Simply copy and paste the toggle helper ID into the trigger input, then turn it ON.
Once your trigger is set up, use the ambient settings to adjust your lights to 50%.
For night lights, use your motion sensor as the state condition and set the lights to 100%.
This should give you the result you’re looking for. If you have more questions or are using the Sensor Light Blueprint, feel free to post them in that thread, and I’ll be happy to assist further.
Blacky 