How long have you had the bike? Are you the original owner?

Just from the looks of it, that bike needs a cleaning from the top down--and I mean a deep-clean--remove the chain and degrease; deep-clean the rear cogs and chainrings. I'd definitely consider servicing all bearings as suggested. Probably could use new cables too. Definitely new brake pads. Maybe new tires--again, it's hard to tell if they're dry-rotted from these fairly blurry photos.