If you truly suspect your oven is not at the proper temperature, the only thing to do is buy or use an oven thermometer, and check--remembering that the temperature will vary from slightly below the set temperature to slightly above as the cooking cycle turns on and off. "Slighty" could mean up to 25 F or so in this context.
If your oven is truly at the wrong temperature, you can either learn to adjust the setting to accommodate, or get it serviced.
All ovens are going to have a natural temperature gradient in the air depending on the position. It will be slightly hotter at the top than the bottom. Hot air rises through a process called convection. Furthermore, idiosyncratic patterns of convection are going to create local hot and cool spots depending on the volume of air flow. These will vary based on the shapes of the items in the oven at any given time.
Side note: so called convection ovens just have a fan or two to increase further the air circulation and minimize the temperature gradient while making the conductive transfer of heat from the air to the food more effective by exposing the food in the oven to a greater volume of air per unit time. That is, the fans power the convection, rather than just the buoyancy of hot air doing so.
However, ovens don't heat just through the heat of the air—they also heat through radiant (infrared) heating from the floor, walls, and ceiling of the oven enclosure. The closer an item is to the enclosure surface--especially the floor for ovens where the heating element or burner is at the bottom. and/or the ceiling if there is a heating element at the top—are going to receive more radiant energy. If there are multiple items (such as trays of cookies) in the oven, they will essentially cast "infrared shadows" on each other, so the items directly exposed to the radiant heat will get much more than those not directly exposed (there is some re-radiation from the items themselves, but lets not get complicated...)
In order to even out these effects, almost all cookie recipes where you have two trays in the oven at the same time recommend swapping the trays between shelves and rotating the front-to-back orientation half way through baking.
If you have the patience, I find that baking only one tray at a time is extremely effective.