How long will the filler effect last?

hello.

These days, I feel like my face has lost a lot of volume as I get older.

I heard that filler treatments are often used to add this kind of facial volume. Is that true?

I've heard that fillers are especially effective for nasolabial folds or sunken cheeks. How effective are they, and

I am also curious about how long it lasts.

I have never had filler injections before. Are there any potential side effects?

Or maybe the duration of the results varies depending on the area...

And the price ranges varied widely.

I wonder if the type of filler used varies from hospital to hospital, or why there is such a huge price difference?

I'm not sure what criteria I should use to choose a filler.

Filler experts, please answer.