ligature or not?

[alfonz19]

First of all: I'm pretty bad in english, but there is no piano forum in Czech languague, where can I ask this question. I hope you'll understand me.

Question: How do I distinguish whether the binding two (or more) same notes should be played as one "long note" or "n" separate notes? You can describe it (if you want) using Moonlight Sonata(first movement) fifth/sixth bar(G1 note).

Moonlight sonata can be viewed at https://www.mfiles.co.uk/Scores/moonlight-movement1.pdf