Hello.
It would be interesting to see the outer surface.

I was looking for juniperi but the spores do not reach these dimensions.

Is there some veins on the outer surface?

Nicolas, you mean these neuroses ?

It really looks like Helvella juniperi, it seems strange that the spores are so short. Vasileios, the two specimens are rather young, maybe it's better to wait some days and try to measure again. Always mount in water!
If the ascoma is young you should choose only the "ripe" spores to be measured. Ripe spores in Helvella have a single large oil drop (small droplets at the poles are always possible), the walls are smooth and rather thick (you should see a double line all around the spore in optical section, i.e. you see the thickness of the wall).
If some spores with pustules occur, these are constantly narrower.
The ectal excipulum also can be similar to H. juniperi, but you should made a little step forward in preparing your mounts: the excipulum should be seen in a section taken perpendicularly to the surfaces (hymenial or abhymenial). In your photos it seems rather viewed "from the outside". So only the terminal cells are clearly seen, but the most important are the deeper ones.
Ciao
Mario

I put the sample on wet paper and took measurements again, and if I tried, I dont found spores longer than 21.

that day I found another collection of Helvella and I looked today. Spores 19-22,5 x 11-12,5.

Vasileios,
for the first collection I think the ascoma is still not fully mature, look in the photo I join (your image): near the upper arrow, an ascus with unripe and small spores, look at the difference with the spore pointed by the lower arrow. It's difficult to have a reliable measurement when the ascoma is collected too young, even if you wait until it's rotten, the spores should never reach the "normal" length.
The second collection seem rather typical for H. juniperi, once again the ascoma is not completely mature but you can see several oblong spores, look at those two into the ascus in the first image with the maximum enlargement. However none of all seem to have the look of the ripe spores, with the usual double-lined wall.
Regards
Mario

Thank you very much Mario, for your time !!!!