Qgis destroyed excel, possibility to repair?

I have an important and urgent question. I had an excel file with several data which I imported into Qgis as a layer. For some reasons I had to change the data type of one coloum so I created a new one and imported data from the first coloumn to the new one in the right data type. That worked well but now I cant open my original excel file anymore. I tried to repair it with the excel-repairing-tool but that didn't work.

Any help? Otherwise my work from the last 3 weeks would be gone ... :(

Thanks a lot!