my car wont shift to 2 gear and it wont accelerate over 20 mph
My car has a manual transmission.
If you are unable to get your car in second gear and it is a manual transmission, there must be something wrong with the transmission. If it goes into first gear, then the clutch and hydraulics are good, so we can rule that out. This would be different if your car is an automatic, as this situation may be better explained in the following paragraph.
When a car won’t go over a certain speed, it is usually in "limp mode." This is a default mode that is part of the PCM’s (powertrain control module) programming to save the vehicle from further damage or to keep you safe. I would expect there to be a Check Engine Light on. Connecting a scanner to retrieve any codes as well as accessing the sensor data is the next step in the diagnosis of your car. If you need an expert to scope out this problem firsthand, a certified professional from YourMechanic can come to your location to pinpoint the cause of the shifting problem.