@oppoa5357982 always make sure that your phone settings are properly setup for your speaker. Check volume etc settings first.
If all of that is properly set but your speaker still does not work, the next thing would be to replace the speaker.
Since iFixit does not yet have a guide for this, use something like [https://www.youtube.com/watch?v=2w-ESUdXiDQ|this video] to replace it. Replacements speaker are readily available at many online stores.
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 a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!