Multi Project or Multi Folders

Hello to all.
I am now approaching the first use of the gitlab system.
Based on how the gitlab suite works, I’m asking the following question.

I don’t know how to organize my sources.
Whether to separate them into projects or whether to have a separate single project with folders.

I am currently using an svn server and the sources are separate folders.

This structure has been made because there is a folder with libraries and or common functions.
These libraries are used in individual executable files.
The same libraries are used to generate the libraries to be used on the system I am implementing.

It seems to me a similar structure to the source management of an operating system. Where it is necessary to release single executable files or single libraries.

Sorry if I didn’t make it clear, but I’m just getting started …