Once he was up 4 pawns (3 of them connected and unopposed!) his main goal basically should have been to trade off pieces as much as possible, because the more material that comes off, the stronger his pawns are (they'd march up the board no sweat against your king). I think your last hope would have been to try and pick off his weak c3 pawn, then avoid trading pieces while trying to blockade his pawns with king and bishops (he'd still have to make big mistakes for you to draw, but keep an eye out for nasty forks and pins you could use).
As for the losing material looks like just a lot of tactical oversight. You probably should put some time into tactics trainer or use a book with puzzles. Seems like several times you didn't take back when he took your pawns, without having any threat or attack as compensation? 4 pawns isn't huge material if you're going by a rigid point scale, but in this position where he has 3 connected passed pawns plus majority on the kingside, he's pretty much a piece up or more (he could lose the exchange or blunder a piece and still be in great shape). This is all my amateur analysis, hopefully other people can give you better, more specific stuff.
I've been losing more and more lately in both blitz and correspondence. In this I'll just focus on correspondence. This is my most recent loss. I didn't lose a huge amount of material but he killed all counter-play and I'm really at a loss as to where I could have gained an advantage. I'm not that great a player but I'm getting better and I hope that a little insight might take me to that next level.