Speaker is not working

@mukuch check all of your settings first. Make sure that you do not have teh "Do Not Disturb" mode on. Next make sure that all of your software is up to date. After that place your phone in safe mode (instructions here) to rule out any issues with third party software etc.

If none of that has any results, replace the speaker and re-evaluate. Sine iFixit does not yet have any guides for that, use something like this video or even this one

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.