In that case, what you're doing wrong is having wrong expectations about doing this.
How do I go about using the Ethernet port for LAN and WiFi for Internet access at the same time?
I already configured my LAN connection to only have an IP address, and a subnet mask, leaving default gateway blank...
As for WiFi, I left them to be automatically assigned...
What did I do wrong? They won't work together.
Light bulbs you shouldn't buy
There are plenty of dimmable LED light bulbs, but make sure you don't buy the ones that flicker when you dial them down.