Have you tried WaveUp?
That is the app that I use, and I love it.
There are lots of adjustments in the settings to get it just right.
Also, if all you need is an app to turn the screen off (not on), then I use Greenify to do that.
Within the settings there is the option to make Greenify your assistant app, and by long pressing your circle navigation button it will turn off your screen.
An added benefit of Greenify is that you can use it to force stop apps that run continuously.
This can save battery life, and be set up to occur automatically or manually.
However, if you use Google Assistant you won't be able to do this, as Google Assistant is your assistant app.
But it works fine for me, as I don't need Google Assistant.
I use WaveUp to turn my screen on (my power button is messed up), and I use Greenify to turn my screen off.
WaveUp has the option to turn the screen off as well.
But as I already had Greenify installed and set up, I left things be as they are.