So I bought that air freshener purely for other purpose, however timer is way too fast for me, is is there some way to slow it down? I'd assume changing some resistor values.

 

You may be in luck. I don't see any epoxy blob or parts with a lot of pins.
There are only 2 capacitors. I am guessing that increasing the value of one of those will increase the time. The other parts may limit how long the time can be.
Try reverse engineering the circuit and post your results here for a better answer.

 

I am guessing that increasing the value of one of those will increase the time.

That would be my guess too. I'd try adding another cap in parallel with C1 or C2. Neither looks to be a polarised type.

 

Is there any writing on U1?

My guess would be that C2 is the more likely candidate for the timing.

 

In this photo I tried to make all writings visible, chip have no readable markings.
Measuring these caps without desoldering will be accurate?
I have multimeter capable of measuring on board.