Hi,
I assume that while shifting, you fully release the accelerator (usually the engine speed will then already be too low for the next gear, unless you're shifting like in Formula 1).
Is the engine speed higher before engaging the higher gear than it is after engaging it, or lower (without any acceleration during the gear shift)?
Briefly: Does the engine speed
decrease when engaging the clutch, or does it increase (no rev-matching when shifting, foot completely off the gas before depressing the clutch for a gear change!)?
If it's lower, you probably need to practice a little more

.
If the engine speed is too high, there may be a problem with the throttle position sensor or the fuel injection pump, which could cause the engine speed to drop too slowly when the accelerator is released; in this case, a jerk when engaging the clutch may be difficult to avoid.
Best regards, Rainer.