Hi ΙππολÏτη
I want help you to correct your translation.
1. Lapis is not a diamond but a stone, milestone or cornerstone, maybe a memorial stone.
2. posuit is the perfect of ponere pono, posui, positum. He or one has setted, layed, established
You must now correct your text, if you don’t risk the rejection
Lupellus
Thank you very much Lupepllus I am really grateful for your help I thought that lapis was a valuable stone (diamond)and I convert the active into passive voice. Thanks again!!