Hi, if the problem is that some gear are hard to shift or they slide while driving, you need to adjust the gear lever. For that, there are 2 bolts on the right side of the gear shift tunnel, on the base.
If you find issues on the 1 or 3 gear, you need to loose these bolts and push the gear lever to the front
If you find issues on the 2 or 4 gear, you need to push it back.
Hope it helps! I had to do it myself after replacing the linkage and the clutch!