Where to learn to improve play in BB/SB?

I don't think those stats are so bad with playing in the blinds. If you don't play any hand in the blinds the stats would be BB/SB -100/-50 per 100. Not sure you follow coaching here and checked our https://forums.pokerstrategy.com/forum/thread.php?threadid=420360 thread. There you can find a lot of information I think.

Cheers,
SDK1987

get janda, applications of NL holdem

the chapters about play OOP are excellent.

Depends on your skill level. If you are still quite beginner and want to focus on blind play, I would definitely skip that book from Janda and just watch some coaching videos about that topic here on PSGY.
If you just open the video section and search for "blind" you will find many videos from many different coaches.

BTW how big of a sample size we are talking about? I think -84bb/100 on big blind is horrible, and that could have something to do with too small sample for positional stats.

hi i actually viewed my stats incorrectly, my BB/100 is actually pretty good it seems,

over 23k sample.

Yup. Still a small sample but that looks a lot better. I think a -35bb/100 winrate on BB is already ok, SB could be a bit better.