List answer with different question type

Hi @seb_cortes and welcome to the ODK community forum !
When you get a chance please take some time to introduce yourself here

How many different available materials do you have ?
Can't you simply have one integer question per material, all in one group ?

If you have too much materials, you can imagine a first repeat to select the materials and a second one asking for each selected material its weight.

We achieve something like that to store species abundance.
In this form you can look at groups "gp_especes" and "gp_abondance" (lines 81 to 100). The first one lists the species and the second one ask the abundance for each one.