Can I transfer money back to my debit card?

From Apple Cash? If so, yes. See the following Apple Support article for information on transferring money from Apple Cash to a debit card or bank account: Transfer money in Apple Cash to your bank account or debit card - Apple Support

Note that there is no fee for transferring to a bank account but there is a small fee for transferring to a debit card. See the following from the about support article:

A 1.5 percent fee (with a minimum fee of $0.25 and a maximum fee of $15) is deducted from the amount of each Instant Transfer.