BaikalHunter25, Your instruction manual has a detailed guide for sight adjustment. Like any gun, moving the rear sight up raises the bullet's point of impact. The sight was preadjusted at the factory so if you are shooting more than a few inches low at 25 yards, it's more likely you than the gun. Anticipating recoil will cause you to pull the muzzle down just as you are squeezing the trigger. This will result in low hits.
Here's a few tips .... before you make any adjustments, have a well experienced shooter try your gun. If you determine it is you and not the gun, don't try to maladjust the sights to compensate for your problems. Instead, try skip loading. This is a great technique where you use "dummy ammo". Have a friend load your magazine with random live and dummy rounds. Each time you squeeze the trigger anticipating a bang, you will see the muzzle take a swan dive on the dummy loads. With awareness and continued practice, your hits will start going in the bullseye. If you don't reload, one of your shooting buddies that does reload can fix you up with a handful of dummy loads that have no primer, no powder, just a case and bullet.