Build over gas, water, electricity, and telephone lines with a garage?

Unfortunately, I can't. My garage has only been there for a month. I'm also "curious" how this will develop over time.

here, a pipe was inserted into the gas line at the built-over section. practically (pipe in pipe) then it was okay for the municipal utilities.

DVGW Worksheet G 459/I

3.1.4 Pipeline routing

House connection lines are to be routed as directly as possible from the supply line to the building. The pipeline routing must be determined so that pipeline construction is unhindered and the route remains accessible in the long term. If house connection lines have to be routed under building parts (e.g. conservatories, garages, etc.) or through cavities, they must be laid in protective pipes in this area. It must be ensured that in the event of a leak at the product end pipe, the gas is vented to the outside. A subsequent overbuilding of a house connection line is not permitted without additional protective measures. Storing materials or planting over house connection lines is also not permitted if this impairs the accessibility, operational safety, and repairability of the house connection.

Regarding your storage question:
I don't know of any shed extension/carport with a concrete slab. Everywhere there are paving stones, and not only tools are stored there.
However:
For good air circulation, gaps are usually incorporated at the bottom and possibly under the roof so that the air can circulate.
I don't know if this information is helpful... Garages actually have even less the characteristic of allowing air to circulate...
Maybe my contribution will help others give you better advice

I see no difference regarding storage between the base plate and the pavement. To my knowledge, the base plate in the garage is not insulated from below and is therefore hardly or only slightly (depending on the type of concrete) protected against rising moisture. However, a roof is usually well ventilated and protects against rain. Thus, it remains relatively dry. But I could be wrong.

Much more against storing sensitive items speaks the fluctuation between cold and heat as well as unwanted guests who like to build a cozy nest with [Weihnachtsengelshaar].

I see no difference regarding storage between slab and pavement. To my knowledge, the slab in the garage is not insulated from below and is therefore hardly or only slightly (depending on the type of concrete) protected from rising damp. However, a roof is usually well ventilated and protects against rain. So it stays relatively dry. But I could be wrong.

What argues much more against storing sensitive items is the fluctuation between cold and heat as well as uninvited guests who like to build a cozy nest with Christmas angel hair.

Thank you for your assessment. The nest-building in the decoration was good... [emoji23]

Additionally, it should be mentioned that precast concrete garages tend to condensation/sweating due to the lack of insulation and are rather poorly ventilated. Furthermore, precast garages are not watertight concrete, meaning water can come up from below and wall connections are not perfectly sealed. I would therefore not place boxes on the floor and first gather experience on the humidity and condensation situation.