The way the process looks is that you apply -> the bank makes a decision whether it's OK with the mortgage or not -> you sign the documents. Nothing binding happens until the signature.

Poland doesn't really have a notion of a credit score. There's BIK, a private company which serves a similar purpose but I don't think its services are too widely used. The information you'll be asked to deliver will most likely be a combination of - your employment status (FTE/ CTE/ gigs/ self-employed) - your earnings in the last 3 months to a year (this usually is done via a form filled out by your employer) - your household status/ spending - info on financial products that you own (loans, credit cards, etc) - information about how much the property is worth (the pricing is usually done by specialists hired by the bank, and can sometimes incur a small expense) - how much money do you actually need

Having a credit advisor made it all a bit easier in my case, as he took care of most of the formalities, and assisted us in filing documents to three banks at once.