You cannot place a city on a tier 1 tile of another city. Hence the order given is incorrect. It should be
1. Move a settler across the rr to the polluted tile then (wait) the piece
2. Sell everything you can from (old) Frankfurt
3. Abandon (old Frankfurt)
please note that the borders redraw placing the polluted tile in German lands. If you did not pre-position the settler, it would run out of movement when it reached the polluted tile.
4. Reactivate the settler and Build (new) Frankfurt
5. Move (old) Frankfurt defenders etc to (new) Frankfurt
1. Move a settler across the rr to the polluted tile then (wait) the piece
2. Sell everything you can from (old) Frankfurt
3. Abandon (old Frankfurt)
please note that the borders redraw placing the polluted tile in German lands. If you did not pre-position the settler, it would run out of movement when it reached the polluted tile.
4. Reactivate the settler and Build (new) Frankfurt
5. Move (old) Frankfurt defenders etc to (new) Frankfurt
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