When wing stalls, lift is reduced so induced drag must also be reduced?
Yes. But the form drag increases more so the overall drag increases. And it's not like you could actually distinguish them anyway.
Stall decrease static pressure at suction side of wing, so I know pressure drag must increase
Well, “suction side” is a bit problematic here, because lift and pressure drag depend on the pressure distribution differently. Lift is produced by low pressure on the top, and that basically ceases in stall, but pressure drag is produced by imperfect pressure recovery around the trailing edge, and that gets worse in stall.
how then induced drag decrease if this is also pressure drag
Induced drag is pressure drag, but not all pressure drag is induced drag.
or how can I distingusih these two drag?
Well, you can't really.
The formula for induced drag, with $\epsilon = 1$, is the minimum drag a passive aerodynamic device must produce to generate lift. Producing more lift violates conservation of momentum and energy—producing upward force, lift, requires accelerating air downward by principle of action and reaction, but then it's kinetic energy increases and if the device does not have additional power input (passive), it comes at expense of the vehicle as drag.
In the non-stalled regime, this formula with added efficiency factor $\epsilon$ plus another term proportional simply to dynamic pressure works well to approximate the drag.
But in the stalled regime the drag is non-linear. You can't use simple formulas to approximate it. So nobody bothers, and therefore nobody cares about which portion of drag is induced and which is parasite—when you do full fluid dynamics calculation, there is simply a pressure field and integrating it results in a force that has a lift and drag component, but the drag is not split to induced and parasite; it just is.