Help! My phone has several issues regarding sound and basic functions

@aishinchi go to your "Voice Memos" app and try to record a memo.

If you cannot - if you don't have the possibility to press on the record button, then most likely you phone is suffering from an audio circuit failure, very common on iPhone 7/7+ specially after a drop.

So unless your phone has suffered from other issues such as liquid damage, this audio circuit issue is the most probable cause for failure.

If your phone is still under warranty, and has not been previously opened, you can have it replaced at Apple.

Otherwise you have to seek the help of a micro-soldering technician. It is a delicate repair, and for sure not a DIY one. If the tech is experienced and has the proper tools, it can be pretty straightforward specially that we've been seeing them and repairing them almost daily. And a proper technician will not just " reflow" the chip (bad practice) or just replace the chips (useless), but actually repair some severed connections to prevent this from happening again in the future.