My car turns on just fine. After a while driving it. The car loses power and it doesn’t want to even hit 10 mph. My check engine light is on, but the machine tells me it’s the oxygen sensors. Can someone help me?
The restricted acceleration and low top speed (with accompanying CEL) sounds very much like the car is going into limp mode to me.
Given the error code is pointing to the oxygen sensors I'm surprised the mechanic is leaning towards overheating unless there are more symptoms that aren't in your question. I'd be looking at the oxygen sensors themselves or something else that is restricting the airflow through the engine.
Depending upon the conditions and how you are driving it 10-15 mins sounds very much like the time the engine takes to come up to temperature where the ECU will be attempting to swap from the cold start fueling to using the dynamic figures from the oxygen sensors to tailor AFR, if it's getting no or out of range readings from the sensors this could be enough to trigger limp mode.