Clutch actuators are consumable items; don't buy a used one! Might be an idea to do a FULL basic setting, rather than missing out an important part, i.e. ADJUST.
RAB
There's no such thing as a good second-hand clutch guide sleeve. Part no. 7 here:
https://volkswagen.7zap.com/en/rdw/lupo++lupo+3l+tdi/lu/2001-231/1/141-141010/
RAB
Most likely the potentiometer of the clutch actuator is beginning to fail. Either buy a new actuator or send the electrical part to Mankmil. See here; https://a2-freun.de/forum/forums/topic/45241-a2-12tdi-gear-selector-not-pushing-down-to-3rd-4th-and-5th-gears/
He will replace the potentiometer with a Hall sensor which is a non-wearing part. English is fine. The second option is the cheapest one and will give a longer life.
RAB