Hi everyone,
I just played this game as black - I'm not really sure what went wrong, but I lost by 18.5 points, so I must have messed up somewhere.

Any comments/advice would be appreciated!
My counting (or lack of it, rather) might be part of the problem - I actually thought I was slightly ahead, so the score at the end came as a bit of a shock.
Looking back on it, there are a few moves I was iffy on:

I wasn't really sure how to handle white's opening, so I just defaulted to making a base for myself. Would moving into the corner be better? Or jumping out?

I felt like that white stone on the 4th line was screaming "slide under me!", but after

,

,

I feel like white got the better deal here - that's a huge corner. Should I have done something different? Maybe S6 would be better, but I'm not sure it would make much difference.

Should I have just blocked downwards? I was trying to stop his lower right from getting too big.
Thanks in advance!