All you can do is go to the training ground and practice using snipers using the 8x scope. The bullet drop in PUBG mobile depends on the speed of the bullet in a major way. So the Kar98k has a higher bullet drop than its peers and needs much more compensation to control it. While the faster M24 does not need that much compensation. On the other hand, AWM, which has the fastest bullet in the game barely needs any because its bullet drops by very little even at a far distant like 300m. In the training ground, you can measure how much adjustment your aiming needs for each gun at different ranges.