magaduccio wrote:My question is how can I access the underneath of the machine?
Simple answer, far from straightforward.
The side panels, outer door panel, counterweight, baskets, filters and so on need removing. The actual tub has to be lifted clear of its base to then have full access to the working components within. There is no other way so don't even go there!
It helps first to simply remove the side panels and run the machine to try to locate the leak first. As once it's in bits you'll never be sure. It's either the main circulation pump, the heater or an overflowing water inlet matrix being the main suspects.
You'd be well advised though to seek local help from a independent repairer. Not really a job for the DIYer to be honest!