According to the website:
5. Portal facilities
A portal building will be constructed around the descent into the tunnel on the Danish and German sides. The portal facilities will connect the tunnel railway and motorway with the upgraded and partly newly built roads and railways in the hinterland. The portal will contain a light grid in the tunnel roof to ensure a smooth transition between the natural light and the light in the tunnel.
Work on the portal buildings on the Danish and German sides began in 2022. They are expected to be finished in 2024 on the Danish side and 2025 for the German side.
This is only for the Danish side. For contrast, /marketwise/will-the-portal-facilities-for-the-de0d9f31eeee
1,000
3.00Construction of the Fehmarnbelt tunnel between Germany and Denmark has hit a milestone with the completion of the first 100m, which accounts for the Danish portal. (source)