Did u update it recently to Oreo? If yes then I would suggest you better hard reset your phone once, it will remove all the problems that you are facing. Don't forget to take backup before formatting. It's always advisable to format your phone after updating it to any MAJOR updates like Oreo or Android P or Q or whtvr.
Thank you for being a part of Samsung community. We apologize for the issue you are facing in the device after update. We would recommend you to follow some troubleshooting steps in order to further isolate what you may be experiencing in your device. Find the troubleshooting steps on the provided link http://www.samsung.com/in/support/skp/faq/1101689. Please let us know what steps you have taken and if you have noticed any changes or improvements as this will help the Community to provide you further troubleshooting steps without repeating any procedure which you may have already followed. Be sure to hit ♡ when you find an answer that works for you.
For Further assistance, you can get in touch with us via Live Chat option by following- http://livechat.support.samsung.com/Customer_new/IN. You can also connect us via Samsung Members web community by following mentioned url-https://community.samsungmembers.com/en_IN#/
