Need some opinions on my first plant

If only someone could help me get an idea on how long til harvest

No can say for sure.
However, judging by the overall morphology and skinny leaf, I'd guess that it will take 10 to 12 weeks from the start of flowering.

Best we can do brah.

Weeze

Is it normal for leaves to start turning yellow pretty fast

Short answer, Yes

Have ya added nutrients & if yea, which type? & stop yer whining he, he..... That's a big azz girl! Actually just posted a jpeg of a nug that I sliced off of a bush this a.m.

I just use LK