wow you have to have some really strong character to play chess, as well as motivation and persistence. 
It actually requires a lot of reading, memory and strategy.
do you ever use an shortcuts like skewers, pins and forks?
I use mostly forks. But as I said before it's a lot around strategy rather than shortcuts. 
i know the ELO is an older rating system but how does that work exactly?
It's a very complex formula. It depends on your current ranking and your opponent's and the game outcome 
what would you say is the strategy you use the most? opening theory?
I use the Ruy Lopez opening most of the time. Else I'd go with Sicilian 
how about the berlin defense? that one is also very dated and proven to be great
My winning rate using that one is usually below my average, hence I tend to not use it