The bridge has washed out and your agent needs to rebuild it before you can keep going!
The bridge is 21 blocks long and 6 blocks wide.
You need to figure out how many blocks you need and make sure the agent has enough dark oak planks.
Make use of the repeat block.
There are many ways to create your bridge. In order to code one common solution, you will need these blocks:
repeat [ ] times
agent turn left
agent place down
agent turn right
agent set block or item [dark oak planks] count [ ] in slot 1
on chat command "bridge"
agent move forward by [ ]
If you are still stuck, go to Hint 2.