Please tell me the benefits of fillers and the precautions before the procedure.

The area between the side of my nose and the front of my cheek looks slightly sunken, making my face appear somewhat flat overall. Since that area stands out whenever I take photos, I am looking into filler treatments. I have heard that the advantage of fillers is that they can restore volume in a relatively short time, but I am curious about what kind of changes I can actually expect. Conversely, I would also like to know the precautions I must be aware of before the procedure. My skin tends to be sensitive, so I am worried that swelling or bruising might last a long time. I am also curious if the appropriate product or injection method varies depending on the treatment area. I want to choose a clinic that thoroughly checks my skin condition and facial structure during the consultation. Could I also receive advance guidance on how to handle any uncomfortable symptoms that may arise after the procedure? I want to find a clinic that explains the methods necessary for my face, rather than simply recommending the treatment unconditionally.