How can a freelancer prove work experience?

Question

Freelance

Friends, suddenly someone went this way: to a freelancer without contracts - pieces of paper - labor - how can you confirm your work experience? If you have a large portfolio and a car of reviews? We want to try to apply for a blue card.
Or bury this idea?

Answer 1

It’s easier to apply for a bluecard with an IT education, even office work experience doesn’t always work, upwork papers won’t help

Answer 2

documentary evidence is needed, otherwise how will it differ from the fictional one?
statement / screenshots from upwork and analogues, for example + bank receipts