While you are driving your car in first gear the transmission suddenly jump out of first gear.
Car Problem Diagnosis
Manual transmission is very complex, we can only provide the most likely possible cause of the car problems, but the real cause can only be determined by actual checking of the transmission it self. When the transmission pops out of the first gear the most likely possible cause is a problem on shift linkage. Shift linkage has a lot to do with the transmission which if out of adjustment it can cause the transmission to pop out of gear.
Possible Cause of Transmission Jump Out of 1st Gear
Out of Adjustments Shift Linkage
All About Auto Recommendation
Bring your car to a reputable auto repair shop specialized in manual transmission and asks the mechanic to check the transmission shift linkage and adjust if necessary. If the problem does not fix by adjusting the shift linkage then you are facing a more serious problem in your transmission and this can only be determined by a professional by means of thorough inspection on the transmission, also this will cost you a lot.