Hard to shift gear huh?
First, check the clutch padel level, if the free play is too much, mean the clutch didn't lift up complete, causing hard to shift other gear. defected clutch cable also will causing the same result.
Second, check the gear shift joint mounding, defected mounding will cause too much of free play, when we shift up the gear, the gear is hard to shift to the correct position.
Third (this is the major one) the gear inside the gear box already crack... in this case, the gear box can't use anymore... ofcourse I hope this will not happen on you ^_^~!
When changing clutch and related part, clutch plate, clutch pad, clutch cover, clutch bearing, clutch cable, flywheel oil seal, gear box oil seal, must change together~!
How to know the clutch is sliping?
1) RPM is rising, but the speed of the car didn't increase any.
2) Engage first gear, rise the RPM to 3000rpm, release the clutch quickly, if the RPM didn't drop or just drop a little 500rpm with out wheel spin.