Realme C53 Phone Low Volume and Performance Problems

Hello, I bought a Realme C53 smartphone from Media Markt. We utilised the device for approximately five months. Ever since I purchased it, the volume on my phone has been disappointingly low, even when turned up to the maximum level. It's so quiet, you can barely hear it. In addition, the device encounters issues such as freezing, lagging, and weak signal reception.

I submitted it for service, and they simply performed an update and cleaning. The problem with the volume is still not resolved. I am extremely unhappy. I would like to return the product since it is still under warranty.

Could you please help me with this problem as soon as you can?