https://www.lexpoint.pt/Default.aspx?PageId=128&ContentId=60...
https://www.vdi.de/news/detail/wer-darf-sich-ingenieur-oder-...
https://engineerscanada.ca/become-an-engineer/use-of-profess...
You can call yourself engineer if you feel like it, however in case it comes to some court case due to liabilities and such, there might be some issues coming up with having Eng in that contract signature.
Many here would probably say that they have never did the exam, and nonetheless use the title, which is as mentioned, not an issue as long as you don't land in court and the validation of title doesn't come up.
Also in most European countries, being an Engineer even if not professionally qualified, automatically means that the person in question took a university degree in engineering, on an university whose engineering degree was certified as such by the government organisation responsible for all engineering professions.