Check the chain for wear , replace if it is , worn chains wear cog teeth so that goes too.

chainring teeth take a bit longer, but they wear too..

These are consumables.. use makes wear. and dirt and under-lubrication speed that process.

dont need to think of Bike shops as the place for only high-end bikes.
they wont be $99. but even a $400 bike in main brand bike shops
will be better made and user friendly..
Trek dealer near by ? Navigator is a comfy ride 1.0 is 8 speed 2.0 adds triple crank
and other features .. 26" wheels are ..