I recently took over the s10+ of my mom, when I transferred my data to the new phone I found something weird, sometimes a little bit of the screen on the bottom just turns black, usually when i restart my phone it disappears, what can I do to fix this?
Make sure everything is updated @Aymanie
Unfortunately it's not easy troubleshooting an intermittent issue.
Try a soft reboot by turning your phone Off and On and if necessary look to clearing the phone's system files via Clear your phone's System Cache Files by turning your phone Off and then from a set series of button presses go into the phone's System Files and clear the cache. No information is lost this way. You may need to insert your headphones or hook upto a computer with your data cable to get to this menu on the phone. https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/
You could try Safe Mode as a generic troubleshooting tip.
Put the phone in Safe Mode which disables your downloaded app's but let's your stock app's keep working. If the issues stop then this highlights a downloaded app as the possible issue. Come out of Safe Mode and start deleting your most recent downloaded app's one at a time until it stops. https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/
If that does not help then try a factory reset after backing up.
If no help then let a Samsung Experience Store or Samsung Service Centre take a look.
Current Phone > Samsung Z Fold³ 5G.