Landwinning translates into English as "reclamation." The English word, though, is a misnomer especially as applied to the Dutch practice of making dry land. That is not reclamation. That is land-winning.
"Toch" serves as an all-purpose affirmation request. It implies (but does not insist) that the accompanying statement is agreeable.
Toen "when," in the past tense.
When speaking in present or future tenses, one says "wanneer." When of the past, one speaks of "toen ik in Amersfoort ging wonen" when I went to live in Amersfoort.