Turkish, perhaps this will help - the basic maintenace schedule for an A320 is thus:
A check = every 400 flight hours. Usually performed on the ramp & will take 4 guys appx 4 hours. This is really just a fluids & gases service along with minor inspections & some function checks.
2A check = 800 hours, includes an A check at the same time. More functions, inspections, filter changes & a couple of boroscope inspections on the engines. This is done in the hangar & will take a day to complete for appx 20 guys. Time limited parts (batteries, slides etc) will normaly be changed at this time.
4A check = 1600 hours, includes 2A & A checks. As above but again a bit more involved.
Most operators combine elements of these 2 checks so that the same check is carried out every 800 hours.
1C check - every 18 months, includes 4A,2A & A checks. Much deeper level of inspections, which will require removal of exterior fairings, interior fixtures, galleys & lavs etc to accomplish. Will take 4 days to a week.
2C check - every 36 months, includes 1C.4A,2A etc etc
3C - can't remember if there is one
4C - big check! Couple of weeks in the shed. Corrosion prevention program will be carried out at the same time.
That lot's from memory , so sorry if details are a bit out but you'll get the idea.
Engines, as mentioned, are not replaced or repaired on the same schedule although these checks will have engine servicing items (meaning fluid & filter changes) & inspections as part of them.
Most of the engine will be an "on condition" item, where it is only replaced (or the engine removed & sent for overhaul) when inspection shows up a defect.
There are some parts however that have a finite life limit, in hours or cycles, at which time they must be replaced. This usually means sending the engine away for overhaul - compressor discs being an example.
Landing gear are much the same. IIRC they are changed after 6 year in the A320's case.
HTH