I cant thank you enough Margaret, I do understand now!

One last question please, is there a "clever" way to calculate the optimal lag period? Ideally in my project, all tasks should be sequential with no delay between them. So when we say that task 4 ('Pre-check') has dependency '7fs-10d' then this means that task 7 (phase 2) can start 10 days after task 4 has finished, correct?

Does it make sense to have a different lag period per server depending on the duration of phase 1? Or the lag period should not be related at all with the actual duration of the tasks of phase 1?

Apologies for the multiple questions, I am newbie and I am struggling a lot!

Thanks a lot!
Nantia