105 is a great groupset, its known as the best bang for the buck.
Relatively lightweight, & durable.
I run 105 on my Cyclocross rigs, talk about taking a beating...

Try not to cross chain, it will happen, you'll lewrn not to. Also try to train yourself to change gear while you pedals are @ 12, & 6 o'clock. You don't need to be coasting to change gears, just be aware when you do it. It all becomes 2nd nature once you ride more often.

Keep this bike, & enjoy it. It not hard to learn how to do maintenance.
If you still feel the need for a SS/fixie, the market is always flooded with them.
Scan CL for one, convert an older road bike.
Its nice to have the gears when you need them.

I wanted to be a cool kid & tried fixed gear, my knees couldn't take the hills, & I wasn't about to take the walk of shame.
I love to climb so I need my gears.
My knees thank me daily. They love spinning @ higher cadences.