Pieter advices are spot on. Like he said, you must validate your economics first and before anything else.

Second, you must validate that you can build your audience. It roughly means what are the acquisition channels you can activate?

Are you connected in the Portuguese startup scene?
On the potential employer side AND on the potential employees side.

Because, indeed, a job board is just a specific case of a market place.

Finally, from the tool point of view side, you can do it with many solutions. An Airtable embedded, sheet2site www.sheet2site.com/ (the @AndreyAzimov great no-code website builder) or, if I may reference my own project, with RoleUp RoleUp.com

I wish you all the best. If you want to talk more about your project, please, feel free to contact me.