Losing power

This sounds like a simple case of idle speed that is too low, and that is often caused by the battery being recently run dead or disconnected. Before we discuss causes that may not exist, go out and drive the car at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. If that does not solve the problem, read and record the diagnostic fault codes. You can do that yourself by cycling the ignition switch from "off" to "run" three times within five seconds without cranking the engine. Leave it in "run", then watch the code numbers show up in the odometer display. You can go here:

https://www.2carpros.com/trouble_codes/obd2/p0200

To see the definitions, or I can interpret them for you.