Project: Convert stable to workshop. What flooring options?

Hello everyone,

I bought a house that has a decommissioned pigsty as an outbuilding. I want to convert this stable, which is 58 sqm, into a workshop. I have already removed the trough; in the middle of the room, there is a concrete platform that is 2 cm high at its lowest point and 12 cm high at its highest point. Now I would preferably like to pour/cast the floor with concrete or something similar.

However, I have the following questions.
1. Which material should I use? Concrete, screed, or concrete screed?
2. Do it myself or hire a company?
3. What costs should I expect?

I could borrow a concrete mixer from an acquaintance, but considering the amount, I suspect that a truck pumping the material in would be much easier.

Here is a photo of the current situation:
I will still remove the remains of the trough fairly evenly.

Sorry, I wanted to write which flooring, but apparently I can no longer change it...

Hello questioner.
The problem you described, regarding the conversion, is relatively easy to solve. A few years ago, I proposed to a local winemaker, with the same initial situation, a plan to turn a former pigsty into a tasting room with catering possibilities. This has been working flawlessly ever since (as expected).
From what I can see in the picture, there is already a floor slab, probably in contact with the ground. The breakouts caused by the removal of the troughs are not a problem for now.
The room is first leveled to determine whether the floor slab has sunk anywhere or if there are bumps over the surface.
The surface is either shot-blasted or intensively ground, then the breakouts (after priming the flanks) are filled with a screed mortar, the entire surface is moistened, provided piece by piece with a mineral bonding bridge, and a cementitious (naturally diffusion-open) bonded screed CT-C35-F5 with a medium thickness of 25mm to 30mm is installed over the whole area.
Since a moisture rise from the backside cannot be ruled out later, a simple paint coating or tiled flooring should be applied as the surface covering.
Because we are working here with a bonded screed and the floor slab cannot warp due to drying, no time will be lost if tiling work begins after 2 weeks.
Elastic (vapor-tight) floor coverings or anything in the direction of wood-based materials (e.g. laminate etc.) are strongly discouraged. That certainly will not work!!
Using a "concrete mixer," as it is used for masonry mortar, is also not recommended!! This would probably result in total damage to the later structure because the mixing principle (here: chute mixer) is not suitable for screeds and the necessary screed strength will very likely not be achieved.
I would hand over the process to a screed installation company, as there are many "pitfalls" hidden in the described structure that a layman simply does not know. Apart from the necessary technology missing for every step.
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Which path you choose is up to you. However, you also bear the risk for a "solo run."
I hope these lines fall on fertile ground and spare you damage in the future.
Ah yes, I almost forgot the cost question.
Calculate about €50/m², which also includes a warranty for the trade.
Regards: KlaRa

Thank you very much for your assessment and the tip to hire a professional. I will do that too, it never felt right to me from the beginning.

: You can let me/us know sometime soon how the further planning looks after the first conversation with the screed specialist company. I repeat once again: As described, the whole thing should actually be easily solvable! Especially if there are no requirements regarding height reference points (meaning: transitioning from the workshop to other rooms or even staircases).