After it restart your device If this doesn't help than install any third party app and force your mobile network to a specific spectrum band of your network supplier If any of this helps you than click on 3 dots and accept it as a solution
If 4g networks are available in your areas than in settings >connectivity>mobile networks> LTE only I think this can help you in improving netwwork speed
Vo nahi bhai I am saying that after clicking a photo with on watermark but if you want to remove it later you can't Other brands provide this feature which are very inferior to samsung
