Hair loss... How to start managing hair loss?

These days, when I wash my hair, dozens of hairs fall out, and my heart sinks.

It seems like the crown area is looking more bare than before, and I feel like I can't leave it like this, so after much thought, I'm posting this.

Actually, this is my first time managing hair loss, so I'm not sure where to start.
I am curious about the principles of hair loss treatment at the clinic, and how painful and effective it is.
I heard that there are injection methods and laser treatments, but is there a treatment that is easy for a beginner like me to receive?

I'd also like to know how to manage hair loss at home to prevent it from falling out. Should I change my shampoo, or would simply changing the time I wash my hair or how I dry it help?

If you have any nutritional supplements or habits you need to be careful about, please let me know, no matter how small.

I'm scared to look in the mirror because of my thin hair, so if you have any valuable advice or a hair care method that has worked for you, please share it with me!
I want to manage it properly before it's too late.