Should I give my passport or original certificates to an agency?

No. Your original passport and certificates prove your identity and your training, so give them only to an official body that asks for them. Keep the originals in a safe place, and send copies when a process asks for them. If an agency asks to hold your passport or original certificates, treat that as a warning sign. Make a digital folder with scans of every document and every receipt, and name each file with its date. Ask for certified copies only when the body that needs them requests them. Keep a log of every payment, with the receipt number and the official channel used. If you ever need a document back, ask for it in writing and keep the reply. Our fake-agent check lists the document warning signs and the questions to ask before you pay anyone.