In challenge 17 I noticed that ‘Lo disfruté’ was used, then a few times this shifted to ‘La disfruté’.
Also, I noticed that in one of the sentences the ‘durante’ was dropped from before ‘el fin de semana’.
And finally, why is it said ‘Vi a su hermano y a mi hermana’ not ‘Vi su hermano y mi hermana’.
I’m interested in understanding and clarifying the reasons why there is the change or an adding/dropping of words in these three instances.
Many thanks!
We’re just trying to expose you to some of the variations you’ll need to get used to - lo/la is a gender thing (not worth worrying about, but worth just noticing) - you can get away with dropping the ‘durante’, so that’s adding to your ear for the language - probably the same kind of thing happening with the ‘Vi a’ - maybe @gabycortinas can shed a little more light on that… 
That’s the Spanish “personal a”, used when a human is the direct object.
Following the SSiW motto, though, I think it’s best if you “Don’t worry about it”! And just listen to lots of sentences and it will become natural when to use it and when not
(But if you do want to look into the grammar, “spanish personal a” should be a reasonable search string.)
Hello Natalie,
What Philip said is correct. You can say “vi la Torre de Londres”, but you have to say “vi A tu hermano en la Torre de Londres”. As for “La/ Lo disfruté”, it depends on gender, though often you would hear two different people using different articles depending on weather they are thinking about the “situation” (fem.) or the object in question that they enjoyed. Finally, “durante” can be dropped as you said without affecting the meaning of the phrase.
Hope this helps!
Gaby