'Shlak' sound when reversing

I have a vehicle written in my signature section, now 36000 km.

My vehicle is manual gear. I changed the gearbox oil at the authorized service last week.

I bought 2 cans of Castrol sytrans V FE 75W-80 oil. It corresponds to 2 liters.

a good oil.

Of course, I check the gear changes every day after the oil is added. there is not much change.

Maybe after the oil put in a certain km, it will show its effect when it gets into the gears.

my question is friends; especially in the morning I practice back gear. maybe 10 times, I put it in reverse gear and get it in neutral. I have never put it in 1st gear and put it back. When I run it for the first time, I press the clutch and put it back on. While doing this 10 times, I had to refresh the clutch at least 5 times.

Is this normal? I know that there is no synchromechine in reverse gear. I am refreshing the clutch again for him.

my other question. Is the 'SHAKE' style sound when I shift into reverse is normal or does it indicate that the reverse gear is worn out?

NOTE: No carting, shaking or gear rubbing sounded while shifting into reverse. Thank goodness.