You can approach this in several ways depending on your preferences like code vs no-code. One option is via a Column Expression using the new column() features:
if (column("material").equals(column("material",1))) {
column("creation",1)
} else {
null
}
It checks if the material number of the current row is equal to the material number of the following row. If so, take the creation date of the following row. If not, leave it empty.
Tip: try to include your data in a workable format to avoid people having to manually type over your data table from a screenshot. People are more inclined to jump in if you make their life easy as well