@EEight There are some myths floating around about the GDPR and the use of cookies. As far as i know you can use cookies without users having to agree to it as long as they are essential to the site and not used to profile users. So a simple session cookie should be fine.
To make the site GDPR compliant you would have to add information to the site where users are informed about what data is processed, how it is processed, what is the legal basis for that and what rights they have about this. Here is the actual text of the GDPR about the information that is required: https://gdpr-info.eu/art-13-gdpr/. I assume the legal basis would be Art. 6(1a) GDPR (given consent), which comes with the right to revoke the consent at any given time.