The shifter linkage will only select third or fourth gear.
Hello. If the shifter is stuck in 3rd and 4th gear then most of the time the linkage is the problem. With the engine off you should be able to move the shifter through all of the gears. If not then the linkage needs to be repaired. If the linkage is fine then the problem may be in the shift fork assembly in the transmission. A mechanic would need to remove the linkage at the transmission and see if it is binding prior to removing it from the transmission. You can have a certified mechanic, such as one from YourMechanic, diagnose your shifting issue to determine what needs to be done.