Same note, two different durations on same beat

I am retyping for the first time a classic guitar sheet and have some doubts:

1) I don't know what is the correct name for the 'same note, same beat, different durations'. What would be the correct terminology for that, and how could I set this into MuseScore?

2) At the firsts beat, how can I place this 'ghost legato' (pardon my ignorance again... how is this called) ?

3) How to place the fingering and strings notation?

many many thanks in advance for your kind and quick support, as always.

Martin