White plays and wins in 3 moves https://lichess.org/gLN7SKpv
- Rg7+ Kh8 2. Bf7 Ra8 3. Rh7#
It was a mistake not to kill the bishop.
The analysis board does checkmate in 5 moves
- Rg7+ Kh8 2. Bf7 Rxf7 3. Rxf7 Kg8 4. Rf1 Kh8 5. Rf8#
Source:
This publication is in my collection "500 chess puzzles. Mate in 5. Advanced & Expert Level."