I lost my German documents. Can I still claim a refund?

Almost always, yes. Your contribution history is stored at the Deutsche Rentenversicherung under your insurance number, and it does not disappear because your paperwork did. A lost insurance number can be recovered with your name, date of birth and place of birth. Missing employment periods can be reconstructed through an account clarification (Kontenklärung), the procedure that matches your record against what employers reported. What you genuinely need fresh are the documents that prove who and where you are today: a valid passport and proof of your current address abroad. Fundsback handles the recovery and the account clarification as part of the refund process, so lost papers slow a case down more often than they stop one.