How to make Ariston Hotpoint FMG 863 SK washing machine to use more water
I doubt that there is a way to do this, unless it is clearly written in the manual. Additional water in my Candy washing machine is used only for additional rinsing cycles and not for washing, therefore it even prolongs the time of washing, which is opposite of what I (and you, it seems) want.

I posted the similar question - whether there is a washing machine on the market that would allow me to low-level program it (e.g. to determine the amount of water as well). Apparently there isn't, but the feature is available in commercial washing machines, for example:

https://www.alibaba.com/product-detail/Front-load-fully-programmable-industrial-50kg_60387387819.html

Note the specs, it says: USB port microprocessor enables to reprogram freely&amp;easily by PC.

Perhaps your service/repair guy has this kind of access to your machine, but I highly doubt it, since it would probably make the energy certification invalid. The best is calling the authorized service shop and ask them.