I’m new to bikes. I feel like I messed my bike up already.

I was cleaning the chain for the first time and I accidentally made it come loose and then I had it on the wrong gear. After getting everything back right, it seems to take more effort to pedal and when I go backwards the chain seems to get caught from the cassette to the rear derailleur.

Let me know if you see anything wrong or if I’m just in my head.