Trade businesses decide on ability. A trial day or a short task shown on video says more than any certificate.
Language is needed on site, above all for safety and for arrangements. A basic level is enough at the start when the business supports the induction.
Many candidates bring practice from construction and fitting out. They get to know German standards and materials in the business.
Firms with their own vehicles and organised journeys have an easier time. Without a driving licence and without transport links it gets hard for candidates.