Great sentence — it is almost perfect!
Original: The big combine cuts wheat and collects grain in one go.
Better: The big combine cuts the wheat and collects the grain in one go.
Why? We add the before "wheat" and "grain" because we are talking about specific wheat and grain. "In one go" means "all at once" or "in one trip." You can also use the word harvests instead of "cuts and collects."
Even simpler: The big combine harvests the wheat.
Nice work — short and clear!