Hi,
its quite hard to tell how many they are inviting, but I would guess its somewhere around 300 in total per year as they are in need for ~30 pilots per year.
Passrate of the first stage is a little bit varying but overall between 35-40% I guess.
Second stage is the simulator screening. Passrate is approx 60-70%.
Third stage is the psychological Assesment, where you have 30-45% passrate.
Last stage is the interview where you have 40-50% passrate.
Overall it is the standard Lufthansa selection with a total passrate below 10%.
All passrates and the crew demaned are just a rough estimated. It is also possible that they will take everyone at a stage on one day and no one on another.
There are 2 really important tasks for the first stage: 1) practise everythin as much as possible at home 2) keep calm and totaly focused on the day.
Good luck.