Yestotally is back? Welcome back~
is it せがたかい？ or せのたかい？ i don't understand what "seno" or "sega" mean!!!
takai = tall so why do i need to put seno or sega in front of it!
"A tall person is standing."
i'm learning via rosettastone and they don't actually explain anything, i should probably look on their forums instead
Well to be simple, both of those are correct. They're both phrases you'd use to describe someone that's tall. like for instance in this sentence: あの背が高い女の子は美人ですね？ (that tall girl is pretty isn't she?) the 'se' is basically for the word "height" and the 'ga' is the particle you'd use for the sentence subject which is in this case is the fact that the person is tall
'no' works for this too because it some cases it works as a replacement for 'ga' another example: 昨日、君は背の高い男子と一緒だったね？(you were with a tall guy yesterday right?)
I'd highly recommend this dude's guide to japanese grammar you'll get rundowns on what all of the particles in japanese mean, how they're used and when they're used. A lot of language learning resources kinda just gloss over the most important thing which is grammar