I have Sora front derailleur.
maybe it's just me, maybe it something else, but I am having problem with it since day one.

First, it does not shift smoothly. I have to push shifter really hard, but it does not shift, I have to push two or three times for it to work. It is not that I use it all the time, but I have had some steep hills yesterday, and really needed to work properly.

Then, either the derailleur is sliding, or something else, -- but overtime it starts to rub the chain. I have taken the bike to shop several times, they have adjusted it, but after 200-300-400 miles the problem is back.

Currently I have 50-3? Sora crankset. I will be replacing it with 105 53-39 later this year.

I am thinking.... maybe I will have to change the derailleur too? Will it solve my problems with shifting and chain rubbing?

Also, my bike is 9 speed bike, is it ok to use 10 speed FRONT derailleur on it?

You may be experiencing troubles with the shifter, the part near in your hand,
not the FD itself..

Take the cable off and test the RD isolated from the rest of the mech.

How do I test it? What signs am I looking for?

use your hand and move the derailer thou it range . does it move ? hard ? then it the derailer the problem but in most cases it the shifter at fault and need replacing. also check the cable and housing which too need to be replace.