Ok, I think you now have to learn how to shift the gears without bad sounds from gear box...
With a little practice, shifting an unsynchronized transmission is relatively easy:
Starting off:
On the flat without a load, do not select the lowest gear. With a 5-speed transmission, you usually start off in 4th gear, but with a 4-speed transmission, you can shift in 3rd gear.
Upshifting:
For example, from 3rd to 4th gear:
1. Depress the clutch, disengage 3rd gear
2. Release the clutch (gear lever in neutral)
3. Depress the clutch, engage 4th gear
4. Release the clutch again
Downshifting:
1. Depress the clutch and disengage gear
2. Release the clutch (gear lever is in neutral)
3. Briefly accelerate
4. Depress the clutch and engage a lower gear
5. Release the clutch
Downshifting is much more difficult than upshifting -
but again, it's just a matter of practice.