Still haven't got the solution in four but I would just like to point out it's an incredible composition. One of the golden rules of chess puzzle compositions is to ensure the position is technically legal, meaning it can be reached from the starting position via legal means, even if the final position is absurd and never actually happening in a real game, like this one.

So... consider that white hasn't lost a single piece yet. Black's pawns must all have reached their destination by advancing, not by capturing and moving onto a different file. So black's a2 pawn started on a7.

Now consider a6 and a7. These pawns must have captured pieces, since they have advanced past black's a2 pawn, which started on a7 and has only moved forwards. Pawns block each other. So both the a-pawns have captured pieces. a-pawn can move to the b-file and back to the a-file, and b-pawn to the a-file. Three captures there.

Also consider d7 and f5. Both of these pawns must have captured at least one piece in order to reach these squares, since there are pawns on d2 and f2, these haven't moved. If they both captured one piece each, then they are the e2 and g2 pawns. That leaves e6 as the h2 pawn, which must have captured three pieces.

That's a total of eight captures. Black has lost eight pieces. By playing suicide chess, it's possible to reach this position legally. So kudos to the composer for that.